Merge branch 'git-lib'

7 files changed, 675 insertions, 787 deletions

diff --git a/lib/app.js b/lib/app.js
index f3b1774..9166eb2 100644
--- a/lib/app.js
+++ b/lib/app.js
@@ -11,7 +11,7 @@ var About = require('./about')
 var Follows = require('./follows')
 var Serve = require('./serve')
 var Render = require('./render')
-var Git = require('./git')
+var Git = require('ssb-git')
 var cat = require('pull-cat')
 var proc = require('child_process')
 var toPull = require('stream-to-pull-stream')
@@ -62,7 +62,7 @@ function App(sbot, config) {
   this.unboxMsg = this.unboxMsg.bind(this)
 
   this.render = new Render(this, this.opts)
-  this.git = new Git(this)
+  this.git = new Git(this.sbot, this.config)
   this.contacts = new Contacts(this.sbot)
   this.follows = new Follows(this.sbot, this.contacts)
 
@@ -101,7 +101,7 @@ App.prototype.error = console.error.bind(console, logPrefix)
 
 App.prototype.unboxMsg = function (msg, cb) {
   var self = this
-  var c = msg.value && msg.value.content
+  var c = msg && msg.value && msg.value.content
   if (typeof c !== 'string') cb(null, msg)
   else self.unboxContent(c, function (err, content) {
     if (err) {
@@ -905,3 +905,78 @@ App.prototype.expandOoo = function (opts, cb) {
     }
   }
 }
+
+App.prototype.getLineComments = function (opts, cb) {
+  // get line comments for a git-update message and git object id.
+  // line comments include message id, commit id and path
+  // but we have message id and git object hash.
+  // look up the git object hash for each line-comment
+  // to verify that it is for the git object file we want
+  var updateId = opts.obj.msg.key
+  var objId = opts.hash
+  var self = this
+  var lineComments = {}
+  pull(
+    self.sbot.backlinks ? self.sbot.backlinks.read({
+      query: [
+        {$filter: {
+          dest: updateId,
+          value: {
+            content: {
+              type: 'line-comment',
+              updateId: updateId,
+            }
+          }
+        }}
+      ]
+    }) : pull(
+      self.sbot.links({
+        dest: updateId,
+        rel: 'updateId',
+        values: true
+      }),
+      pull.filter(function (msg) {
+        var c = msg && msg.value && msg.value.content
+        return c && c.type === 'line-comment'
+          && c.updateId === updateId
+      })
+    ),
+    paramap(function (msg, cb) {
+      var c = msg.value.content
+      self.git.getObjectAtPath({
+        msg: updateId,
+        obj: c.commitId,
+        path: c.filePath,
+      }, function (err, info) {
+        if (err) return cb(err)
+        cb(null, {
+          obj: info.obj,
+          hash: info.hash,
+          msg: msg,
+        })
+      })
+    }, 4),
+    pull.filter(function (info) {
+      return info.hash === objId
+    }),
+    pull.drain(function (info) {
+      lineComments[info.msg.value.content.line] = info
+    }, function (err) {
+      cb(err, lineComments)
+    })
+  )
+}
+
+App.prototype.getThread = function (msg) {
+  return cat([
+    pull.once(msg),
+    this.sbot.backlinks ? this.sbot.backlinks.read({
+      query: [
+        {$filter: {dest: msg.key}}
+      ]
+    }) : this.sbot.links({
+      dest: msg.key,
+      values: true
+    })
+  ])
+}
diff --git a/lib/git.js b/lib/git.js
deleted file mode 100644
index cfcea9e..0000000
--- a/lib/git.js
+++ /dev/null
@@ -1,667 +0,0 @@
-var pull = require('pull-stream')
-var paramap = require('pull-paramap')
-var lru = require('hashlru')
-var memo = require('asyncmemo')
-var u = require('./util')
-var packidx = require('pull-git-packidx-parser')
-var Reader = require('pull-reader')
-var toPull = require('stream-to-pull-stream')
-var zlib = require('zlib')
-var looper = require('looper')
-var multicb = require('multicb')
-var kvdiff = require('pull-kvdiff')
-
-var ObjectNotFoundError = u.customError('ObjectNotFoundError')
-
-var types = {
-  blob: true,
-  commit: true,
-  tree: true,
-}
-var emptyBlobHash = 'e69de29bb2d1d6434b8b29ae775ad8c2e48c5391'
-
-module.exports = Git
-
-function Git(app) {
-  this.app = app
-
-  this.findObject = memo({
-    cache: lru(5),
-    asString: function (opts) {
-      return opts.obj + opts.headMsgId
-    }
-  }, this._findObject.bind(this))
-
-  this.findObjectInMsg = memo({
-    cache: lru(5),
-    asString: function (opts) {
-      return opts.obj + opts.msg
-    }
-  }, this._findObjectInMsg.bind(this))
-
-  this.getPackIndex = memo({
-    cache: lru(4),
-    asString: JSON.stringify
-  }, this._getPackIndex.bind(this))
-}
-
-// open, read, buffer and callback an object
-Git.prototype.getObject = function (opts, cb) {
-  var self = this
-  self.openObject(opts, function (err, obj) {
-    if (err) return cb(err)
-    pull(
-      self.readObject(obj),
-      u.pullConcat(cb)
-    )
-  })
-}
-
-// get a message that pushed an object
-Git.prototype.getObjectMsg = function (opts, cb) {
-  this.findObject(opts, function (err, loc) {
-    if (err) return cb(err)
-    cb(null, loc.msg)
-  })
-}
-
-Git.prototype.openObject = function (opts, cb) {
-  var self = this
-  self.findObjectInMsg(opts, function (err, loc) {
-    if (err) return cb(err)
-    self.app.ensureHasBlobs([loc.packLink], function (err) {
-      if (err) return cb(err)
-      cb(null, {
-        type: opts.type,
-        length: opts.length,
-        offset: loc.offset,
-        next: loc.next,
-        packLink: loc.packLink,
-        idx: loc.idx,
-        msg: loc.msg,
-      })
-    })
-  })
-}
-
-Git.prototype.readObject = function (obj) {
-  if (obj.offset === obj.next) return pull.empty()
-  return pull(
-    this.app.readBlobSlice(obj.packLink, {start: obj.offset, end: obj.next}),
-    this.decodeObject({
-      type: obj.type,
-      length: obj.length,
-      packLink: obj.packLink,
-      idx: obj.idx,
-    })
-  )
-}
-
-// find which packfile contains a git object, and where in the packfile it is
-// located
-Git.prototype._findObject = function (opts, cb) {
-  if (!opts.headMsgId) return cb(new TypeError('missing head message id'))
-  if (!opts.obj) return cb(new TypeError('missing object id'))
-  var self = this
-  var objId = opts.obj
-  if (objId === emptyBlobHash) {
-    // special case: the empty blob may be found anywhere
-    self.app.getMsgDecrypted(opts.headMsgId, function (err, msg) {
-      if (err) return cb(err)
-      return cb(null, {
-        offset: 0,
-        next: 0,
-        packLink: null,
-        idx: null,
-        msg: msg,
-      })
-    })
-  }
-  self.findObjectMsgs(opts, function (err, msgs) {
-    if (err) return cb(err)
-    if (msgs.length === 0)
-      return cb(new ObjectNotFoundError('unable to find git object ' + objId))
-    self.findObjectInMsgs(objId, msgs, cb)
-  })
-}
-
-Git.prototype._findObjectInMsg = function (opts, cb) {
-  if (!opts.msg) return cb(new TypeError('missing message id'))
-  if (!opts.obj) return cb(new TypeError('missing object id'))
-  var self = this
-  self.app.getMsgDecrypted(opts.msg, function (err, msg) {
-    if (err) return cb(err)
-    self.findObjectInMsgs(opts.obj, [msg], cb)
-  })
-}
-
-Git.prototype.findObjectInMsgs = function (objId, msgs, cb) {
-  var self = this
-  var objIdBuf = new Buffer(objId, 'hex')
-  // if blobs may need to be fetched, try to ask the user about as many of them
-  // at one time as possible
-  var packidxs = [].concat.apply([], msgs.map(function (msg) {
-    var c = msg.value.content
-    var idxs = u.toArray(c.indexes).map(u.toLink)
-    return u.toArray(c.packs).map(u.toLink).map(function (pack, i) {
-      var idx = idxs[i]
-      if (pack && idx) return {
-        msg: msg,
-        packLink: pack,
-        idxLink: idx,
-      }
-    })
-  })).filter(Boolean)
-  var blobLinks = packidxs.length === 1
-    ? [packidxs[0].idxLink, packidxs[0].packLink]
-    : packidxs.map(function (packidx) {
-      return packidx.idxLink
-    })
-  self.app.ensureHasBlobs(blobLinks, function (err) {
-    if (err) return cb(err)
-    pull(
-      pull.values(packidxs),
-      paramap(function (pack, cb) {
-        self.getPackIndex(pack.idxLink, function (err, idx) {
-          if (err) return cb(err)
-          var offset = idx.find(objIdBuf)
-          if (!offset) return cb()
-          cb(null, {
-            offset: offset.offset,
-            next: offset.next,
-            packLink: pack.packLink,
-            idx: idx,
-            msg: pack.msg,
-          })
-        })
-      }, 4),
-      pull.filter(),
-      pull.take(1),
-      pull.collect(function (err, offsets) {
-        if (err) return cb(err)
-        if (offsets.length === 0)
-          return cb(new ObjectNotFoundError('unable to find git object '
-            + objId + ' in ' + msgs.length + ' messages'))
-        cb(null, offsets[0])
-      })
-    )
-  })
-}
-
-// given an object id and ssb msg id, get a set of messages of which at least one pushed the object.
-Git.prototype.findObjectMsgs = function (opts, cb) {
-  var self = this
-  var id = opts.obj
-  var headMsgId = opts.headMsgId
-  var ended = false
-  var waiting = 0
-  var maybeMsgs = []
-
-  function cbOnce(err, msgs) {
-    if (ended) return
-    ended = true
-    cb(err, msgs)
-  }
-
-  function objectMatches(commit) {
-    return commit && (commit === id || commit.sha1 === id)
-  }
-
-  if (!headMsgId) return cb(new TypeError('missing head message id'))
-  if (!u.isRef(headMsgId))
-    return cb(new TypeError('bad head message id \'' + headMsgId + '\''))
-
-  ;(function getMsg(id) {
-    waiting++
-    self.app.getMsgDecrypted(id, function (err, msg) {
-      waiting--
-      if (ended) return
-      if (err && err.name == 'NotFoundError')
-        return cbOnce(new Error('missing message ' + headMsgId))
-      if (err) return cbOnce(err)
-      var c = msg.value.content
-      if (typeof c === 'string')
-        return cbOnce(new Error('unable to decrypt message ' + msg.key))
-      if ((u.toArray(c.object_ids).some(objectMatches))
-      || (u.toArray(c.tags).some(objectMatches))
-      || (u.toArray(c.commits).some(objectMatches))) {
-        // found the object
-        return cbOnce(null, [msg])
-      } else if (!c.object_ids) {
-        // the object might be here
-        maybeMsgs.push(msg)
-      }
-      // traverse the DAG to keep looking for the object
-      u.toArray(c.repoBranch).filter(u.isRef).forEach(getMsg)
-      if (waiting === 0) {
-        cbOnce(null, maybeMsgs)
-      }
-    })
-  })(headMsgId)
-}
-
-Git.prototype._getPackIndex = function (idxBlobLink, cb) {
-  pull(this.app.readBlob(idxBlobLink), packidx(cb))
-}
-
-var objectTypes = [
-  'none', 'commit', 'tree', 'blob',
-  'tag', 'unused', 'ofs-delta', 'ref-delta'
-]
-
-function readTypedVarInt(reader, cb) {
-  var type, value, shift
-  reader.read(1, function (end, buf) {
-    if (ended = end) return cb(end)
-    var firstByte = buf[0]
-    type = objectTypes[(firstByte >> 4) & 7]
-    value = firstByte & 15
-    shift = 4
-    checkByte(firstByte)
-  })
-
-  function checkByte(byte) {
-    if (byte & 0x80)
-      reader.read(1, gotByte)
-    else
-      cb(null, type, value)
-  }
-
-  function gotByte(end, buf) {
-    if (ended = end) return cb(end)
-    var byte = buf[0]
-    value += (byte & 0x7f) << shift
-    shift += 7
-    checkByte(byte)
-  }
-}
-
-function readVarInt(reader, cb) {
-  var value = 0, shift = 0
-  reader.read(1, function gotByte(end, buf) {
-    if (ended = end) return cb(end)
-    var byte = buf[0]
-    value += (byte & 0x7f) << shift
-    shift += 7
-    if (byte & 0x80)
-      reader.read(1, gotByte)
-    else
-      cb(null, value)
-  })
-}
-
-function inflate(read) {
-  return toPull(zlib.createInflate())(read)
-}
-
-Git.prototype.decodeObject = function (opts) {
-  var self = this
-  var packLink = opts.packLink
-  return function (read) {
-    var reader = Reader()
-    reader(read)
-    return u.readNext(function (cb) {
-      readTypedVarInt(reader, function (end, type, length) {
-        if (end === true) cb(new Error('Missing object type'))
-        else if (end) cb(end)
-        else if (type === 'ref-delta') getObjectFromRefDelta(length, cb)
-        else if (opts.type && type !== opts.type)
-          cb(new Error('expected type \'' + opts.type + '\' ' +
-            'but found \'' + type + '\''))
-        else if (opts.length && length !== opts.length)
-          cb(new Error('expected length ' + opts.length + ' ' +
-            'but found ' + length))
-          else cb(null, inflate(reader.read()))
-      })
-    })
-
-    function getObjectFromRefDelta(length, cb) {
-      reader.read(20, function (end, sourceHash) {
-        if (end) return cb(end)
-        var inflatedReader = Reader()
-        pull(reader.read(), inflate, inflatedReader)
-        readVarInt(inflatedReader, function (err, expectedSourceLength) {
-          if (err) return cb(err)
-          readVarInt(inflatedReader, function (err, expectedTargetLength) {
-            if (err) return cb(err)
-            var offset = opts.idx.find(sourceHash)
-            if (!offset) return cb(null, 'missing source object ' +
-              sourcehash.toString('hex'))
-            var readSource = pull(
-              self.app.readBlobSlice(opts.packLink, {
-                start: offset.offset,
-                end: offset.next
-              }),
-              self.decodeObject({
-                type: opts.type,
-                length: expectedSourceLength,
-                packLink: opts.packLink,
-                idx: opts.idx
-              })
-            )
-            cb(null, patchObject(inflatedReader, length, readSource, expectedTargetLength))
-          })
-        })
-      })
-    }
-  }
-}
-
-function readOffsetSize(cmd, reader, readCb) {
-  var offset = 0, size = 0
-
-  function addByte(bit, outPos, cb) {
-    if (cmd & (1 << bit))
-      reader.read(1, function (err, buf) {
-        if (err) readCb(err)
-        else cb(buf[0] << (outPos << 3))
-      })
-    else
-      cb(0)
-  }
-
-  addByte(0, 0, function (val) {
-    offset = val
-    addByte(1, 1, function (val) {
-      offset |= val
-      addByte(2, 2, function (val) {
-        offset |= val
-        addByte(3, 3, function (val) {
-          offset |= val
-          addSize()
-        })
-      })
-    })
-  })
-  function addSize() {
-    addByte(4, 0, function (val) {
-      size = val
-      addByte(5, 1, function (val) {
-        size |= val
-        addByte(6, 2, function (val) {
-          size |= val
-          readCb(null, offset, size || 0x10000)
-        })
-      })
-    })
-  }
-}
-
-function patchObject(deltaReader, deltaLength, readSource, targetLength) {
-  var srcBuf
-  var ended
-
-  return u.readNext(function (cb) {
-    pull(readSource, u.pullConcat(function (err, buf) {
-      if (err) return cb(err)
-      srcBuf = buf
-      cb(null, read)
-    }))
-  })
-
-  function read(abort, cb) {
-    if (ended) return cb(ended)
-    deltaReader.read(1, function (end, dBuf) {
-      if (ended = end) return cb(end)
-      var cmd = dBuf[0]
-      if (cmd & 0x80)
-        // skip a variable amount and then pass through a variable amount
-        readOffsetSize(cmd, deltaReader, function (err, offset, size) {
-          if (err) return earlyEnd(err)
-          var buf = srcBuf.slice(offset, offset + size)
-          cb(end, buf)
-        })
-      else if (cmd)
-        // insert `cmd` bytes from delta
-        deltaReader.read(cmd, cb)
-      else
-        cb(new Error("unexpected delta opcode 0"))
-    })
-
-    function earlyEnd(err) {
-      cb(err === true ? new Error('stream ended early') : err)
-    }
-  }
-}
-
-var gitNameRegex = /^(.*) <(([^>@]*)(@[^>]*)?)> (.*) (.*)$/
-function parseName(line) {
-  var m = gitNameRegex.exec(line)
-  if (!m) return null
-  return {
-    name: m[1],
-    email: m[2],
-    localpart: m[3],
-    feed: u.isRef(m[4]) && m[4] || undefined,
-    date: new Date(m[5] * 1000),
-    tz: m[6],
-  }
-}
-
-Git.prototype.getCommit = function (obj, cb) {
-  pull(this.readObject(obj), u.pullConcat(function (err, buf) {
-    if (err) return cb(err)
-    var commit = {
-      msg: obj.msg,
-      parents: [],
-    }
-    var authorLine, committerLine
-    var lines = buf.toString('utf8').split('\n')
-    for (var line; (line = lines.shift()); ) {
-      var parts = line.split(' ')
-      var prop = parts.shift()
-      var value = parts.join(' ')
-      switch (prop) {
-        case 'tree':
-          commit.tree = value
-          break
-        case 'parent':
-          commit.parents.push(value)
-          break
-        case 'author':
-          authorLine = value
-          break
-        case 'committer':
-          committerLine = value
-          break
-        case 'gpgsig':
-          var sigLines = [value]
-          while (lines[0] && lines[0][0] == ' ')
-            sigLines.push(lines.shift().slice(1))
-          commit.gpgsig = sigLines.join('\n')
-          break
-        default:
-          return cb(new TypeError('unknown git object property ' + prop))
-      }
-    }
-    commit.committer = parseName(committerLine)
-    if (authorLine !== committerLine) commit.author = parseName(authorLine)
-    commit.body = lines.join('\n')
-    cb(null, commit)
-  }))
-}
-
-Git.prototype.getTag = function (obj, cb) {
-  pull(this.readObject(obj), u.pullConcat(function (err, buf) {
-    if (err) return cb(err)
-    var tag = {
-      msg: obj.msg,
-    }
-    var authorLine, tagterLine
-    var lines = buf.toString('utf8').split('\n')
-    for (var line; (line = lines.shift()); ) {
-      var parts = line.split(' ')
-      var prop = parts.shift()
-      var value = parts.join(' ')
-      switch (prop) {
-        case 'object':
-          tag.object = value
-          break
-        case 'type':
-          if (!types[value])
-            return cb(new TypeError('unknown git object type ' + type))
-          tag.type = value
-          break
-        case 'tag':
-          tag.tag = value
-          break
-        case 'tagger':
-          tag.tagger = parseName(value)
-          break
-        default:
-          return cb(new TypeError('unknown git object property ' + prop))
-      }
-    }
-    tag.body = lines.join('\n')
-    cb(null, tag)
-  }))
-}
-
-function readCString(reader, cb) {
-  var chars = []
-  var loop = looper(function () {
-    reader.read(1, next)
-  })
-  function next(err, ch) {
-    if (err) return cb(err)
-    if (ch[0] === 0) return cb(null, Buffer.concat(chars).toString('utf8'))
-    chars.push(ch)
-    loop()
-  }
-  loop()
-}
-
-Git.prototype.readTree = function (obj) {
-  var self = this
-  var reader = Reader()
-  reader(this.readObject(obj))
-  return function (abort, cb) {
-    if (abort) return reader.abort(abort, cb)
-    readCString(reader, function (err, str) {
-      if (err) return cb(err)
-      var parts = str.split(' ')
-      var mode = parseInt(parts[0], 8)
-      var name = parts.slice(1).join(' ')
-      reader.read(20, function (err, hash) {
-        if (err) return cb(err)
-        cb(null, {
-          name: name,
-          mode: mode,
-          hash: hash.toString('hex'),
-          type: mode === 0040000 ? 'tree' :
-                mode === 0160000 ? 'commit' : 'blob',
-        })
-      })
-    })
-  }
-}
-
-Git.prototype.readCommitChanges = function (commit) {
-  var self = this
-  return u.readNext(function (cb) {
-    var done = multicb({pluck: 1})
-    commit.parents.forEach(function (rev) {
-      var cb = done()
-      self.getObjectMsg({
-        obj: rev,
-        headMsgId: commit.msg.key,
-        type: 'commit',
-      }, function (err, msg) {
-        if (err) return cb(err)
-        self.openObject({
-          obj: rev,
-          msg: msg.key,
-        }, function (err, obj) {
-          if (err) return cb(err)
-          self.getCommit(obj, cb)
-        })
-      })
-    })
-    done()(null, commit)
-    done(function (err, commits) {
-      if (err) return cb(err)
-      var done = multicb({pluck: 1})
-      commits.forEach(function (commit) {
-        var cb = done()
-        if (!commit.tree) return cb(null, pull.empty())
-        self.getObjectMsg({
-          obj: commit.tree,
-          headMsgId: commit.msg.key,
-          type: 'tree',
-        }, function (err, msg) {
-          if (err) return cb(err)
-          self.openObject({
-            obj: commit.tree,
-            msg: commit.msg.key,
-          }, cb)
-        })
-      })
-      done(function (err, trees) {
-        if (err) return cb(err)
-        cb(null, self.diffTreesRecursive(trees))
-      })
-    })
-  })
-}
-
-Git.prototype.diffTrees = function (objs) {
-  var self = this
-  return pull(
-    kvdiff(objs.map(function (obj) {
-      return self.readTree(obj)
-    }), 'name'),
-    pull.map(function (item) {
-      var diff = item.diff || {}
-      var head = item.values[item.values.length-1]
-      var created = true
-      for (var k = 0; k < item.values.length-1; k++)
-        if (item.values[k]) created = false
-      return {
-        name: item.key,
-        hash: item.values.map(function (val) { return val.hash }),
-        mode: diff.mode,
-        type: item.values.map(function (val) { return val.type }),
-        deleted: !head,
-        created: created
-      }
-    })
-  )
-}
-
-Git.prototype.diffTreesRecursive = function (objs) {
-  var self = this
-  return pull(
-    self.diffTrees(objs),
-    paramap(function (item, cb) {
-      if (!item.type.some(function (t) { return t === 'tree' }))
-        return cb(null, [item])
-      var done = multicb({pluck: 1})
-      item.type.forEach(function (type, i) {
-        var cb = done()
-        if (type !== 'tree') return cb(null, pull.once(item))
-        var hash = item.hash[i]
-        self.getObjectMsg({
-          obj: hash,
-          headMsgId: objs[i].msg.key,
-        }, function (err, msg) {
-          if (err) return cb(err)
-          self.openObject({
-            obj: hash,
-            msg: msg.key,
-          }, cb)
-        })
-      })
-      done(function (err, objs) {
-        if (err) return cb(err)
-        cb(null, pull(
-          self.diffTreesRecursive(objs),
-          pull.map(function (f) {
-            f.name = item.name + '/' + f.name
-            return f
-          })
-        ))
-      })
-    }, 4),
-    pull.flatten()
-  )
-}
diff --git a/lib/render-msg.js b/lib/render-msg.js
index d4ad670..1603d24 100644
--- a/lib/render-msg.js
+++ b/lib/render-msg.js
@@ -10,6 +10,7 @@ function RenderMsg(render, app, msg, opts) {
   this.render = render
   this.app = app
   this.msg = msg
+  this.serve = opts.serve
   this.value = msg && msg.value || {}
   var content = this.value.content
   this.c = content || {}
@@ -20,6 +21,13 @@ function RenderMsg(render, app, msg, opts) {
   this.shouldWrap = this.opts.wrap !== false
 }
 
+RenderMsg.prototype.getMsg = function (id, cb) {
+  if (!id) return cb()
+  return this.serve
+    ? this.serve.getMsgDecryptedMaybeOoo(id, cb)
+    : this.app.getMsgDecryptedOoo(id, cb)
+}
+
 RenderMsg.prototype.toUrl = function (href) {
   return this.render.toUrl(href)
 }
@@ -287,6 +295,7 @@ RenderMsg.prototype.message = function (cb) {
     case 'talenet-idea-comment':
     case 'talenet-idea-comment_reply': return this.ideaComment(cb)
     case 'about-resource': return this.aboutResource(cb)
+    case 'line-comment': return this.lineComment(cb)
     default: return this.object(cb)
   }
 }
@@ -1638,3 +1647,33 @@ RenderMsg.prototype.aboutResource = function (cb) {
     h('blockquote', {innerHTML: self.render.markdown(self.c.description)})
   ), cb)
 }
+
+RenderMsg.prototype.lineComment = function (cb) {
+  var self = this
+  var done = multicb({pluck: 1, spread: true})
+  self.link(self.c.repo, done())
+  self.getMsg(self.c.updateId, done())
+  done(function (err, repoLink, updateMsg) {
+    if (err) return cb(err)
+    return self.wrap(h('div',
+      h('div', h('small', '> ',
+        repoLink, ' ',
+        h('a', {
+          href: self.toUrl(self.c.updateId)
+        },
+          updateMsg
+            ? htime(new Date(updateMsg.value.timestamp))
+            : String(self.c.updateId)
+        ), ' ',
+        h('a', {
+          href: self.toUrl('/git/commit/' + self.c.commitId + '?msg=' + encodeURIComponent(self.c.updateId))
+        }, String(self.c.commitId).substr(0, 8)), ' ',
+        h('a', {
+          href: self.toUrl('/git/line-comment/' +
+            encodeURIComponent(self.msg.key || JSON.stringify(self.msg)))
+        }, h('code', self.c.filePath + ':' + self.c.line))
+      )),
+      self.c.text ?
+        h('div', {innerHTML: self.render.markdown(self.c.text)}) : ''), cb)
+  })
+}
diff --git a/lib/serve.js b/lib/serve.js
index 77cfdb4..5ba0004 100644
--- a/lib/serve.js
+++ b/lib/serve.js
@@ -21,6 +21,10 @@ var htime = require('human-time')
 var ph = require('pull-hyperscript')
 var emojis = require('emoji-named-characters')
 var jpeg = require('jpeg-autorotate')
+var Catch = require('pull-catch')
+var Diff = require('diff')
+var split = require('pull-split')
+var utf8 = require('pull-utf8-decoder')
 
 module.exports = Serve
 
@@ -76,7 +80,7 @@ Serve.prototype.go = function () {
     if (auth) {
       var a = auth.split(' ')
       if (a[0] == 'Basic') {
-	tok = Buffer.from(a[1],'base64').toString('ascii')
+        tok = Buffer.from(a[1],'base64').toString('ascii')
       }
     }
     if (tok != authtok) {
@@ -537,7 +541,7 @@ Serve.prototype.advsearch = function (ext) {
               ph('td', ['#', ph('input', {name: 'channel', placeholder: 'channel',
                 class: 'id-input',
                 value: q.channel || ''})
-	      ])
+              ])
             ]),
             ph('tr', [
               ph('td', {colspan: 2}, [
@@ -550,8 +554,8 @@ Serve.prototype.advsearch = function (ext) {
       hasQuery && pull(
         self.app.advancedSearch(q),
         self.renderThread({
-	  feed: q.source,
-	}),
+          feed: q.source,
+        }),
         self.wrapMessages()
       )
     ]),
@@ -577,7 +581,7 @@ Serve.prototype.live = function (ext) {
       self.app.sbot.createLogStream(opts),
       self.app.render.renderFeeds({
         withGt: true,
-	filter: q.filter,
+        filter: q.filter,
       }),
       pull.map(u.toHTML)
     )),
@@ -1013,57 +1017,71 @@ function threadHeads(msgs, rootId) {
   }))
 }
 
-Serve.prototype.id = function (id, path) {
+Serve.prototype.streamThreadWithComposer = function (opts) {
   var self = this
-  if (self.query.raw != null) return self.rawId(id)
-
-  this.getMsgDecryptedMaybeOoo(id, function (err, rootMsg) {
-    if (err && err.name === 'NotFoundError') err = null, rootMsg = {
-      key: id, value: {content: false}}
-    if (err) return self.respond(500, err.stack || err)
-    var rootContent = rootMsg && rootMsg.value && rootMsg.value.content
-    var recps = rootContent && rootContent.recps
-      || (rootMsg.value.private
-        ? [rootMsg.value.author, self.app.sbot.id].filter(uniques())
-        : undefined)
-    var threadRootId = rootContent && rootContent.root || id
-    var channel
+  var id = opts.root
+  return ph('table', {class: 'ssb-msgs'}, u.readNext(next))
+  function next(cb) {
+    self.getMsgDecryptedMaybeOoo(id, function (err, rootMsg) {
+      if (err && err.name === 'NotFoundError') err = null, rootMsg = {
+        key: id, value: {content: false}}
+      if (err) return cb(new Error(err.stack))
+      if (!rootMsg) {
+        console.log('id', id, 'opts', opts)
+      }
+      var rootContent = rootMsg && rootMsg.value && rootMsg.value.content
+      var recps = rootContent && rootContent.recps
+        || (rootMsg.value.private
+          ? [rootMsg.value.author, self.app.sbot.id].filter(uniques())
+          : undefined)
+      var threadRootId = rootContent && rootContent.root || id
+      var channel = opts.channel
 
-    pull(
-      cat([pull.once(rootMsg), self.app.sbot.links({dest: id, values: true})]),
-      pull.unique('key'),
-      self.app.unboxMessages(),
-      pull.through(function (msg) {
-        var c = msg && msg.value.content
-        if (!channel && c.channel) channel = c.channel
-      }),
-      pull.collect(function (err, links) {
-        if (err) return gotLinks(err)
-        if (!self.useOoo) return gotLinks(null, links)
-        self.app.expandOoo({msgs: links, dest: id}, gotLinks)
-      })
-    )
-    function gotLinks(err, links) {
-      if (err) return self.respond(500, err.stack || err)
       pull(
-        pull.values(sort(links)),
-        self.renderThread({
-          msgId: id,
-        }),
-        self.wrapMessages(),
-        self.wrapThread({
-          recps: recps,
-          root: threadRootId,
-          post: id,
-          branches: threadHeads(links, threadRootId),
-          postBranches: threadRootId !== id && threadHeads(links, id),
-          channel: channel,
+        cat([pull.once(rootMsg), self.app.sbot.links({dest: id, values: true})]),
+        pull.unique('key'),
+        self.app.unboxMessages(),
+        pull.through(function (msg) {
+          var c = msg && msg.value.content
+          if (!channel && c.channel) channel = c.channel
         }),
-        self.wrapPage(id),
-        self.respondSink(200)
+        pull.collect(function (err, links) {
+          if (err) return gotLinks(err)
+          if (!self.useOoo) return gotLinks(null, links)
+          self.app.expandOoo({msgs: links, dest: id}, gotLinks)
+        })
       )
-    }
-  })
+      function gotLinks(err, links) {
+        if (err) return cb(new Error(err.stack))
+        cb(null, pull(
+          pull.values(sort(links)),
+          self.renderThread({
+            msgId: id,
+          }),
+          self.wrapMessages(),
+          self.wrapThread({
+            recps: recps,
+            root: threadRootId,
+            post: id,
+            branches: threadHeads(links, threadRootId),
+            postBranches: threadRootId !== id && threadHeads(links, id),
+            placeholder: opts.placeholder,
+            channel: channel,
+          })
+        ))
+      }
+    })
+  }
+}
+
+Serve.prototype.id = function (id, path) {
+  var self = this
+  if (self.query.raw != null) return self.rawId(id)
+  pull(
+    self.streamThreadWithComposer({root: id}),
+    self.wrapPage(id),
+    self.respondSink(200)
+  )
 }
 
 Serve.prototype.userFeed = function (id, path) {
@@ -1273,6 +1291,7 @@ Serve.prototype.renderThread = function (opts) {
       msgId: opts && opts.msgId,
       filter: this.query.filter,
       limit: Number(this.query.limit),
+      serve: this,
     }),
     pull.map(u.toHTML)
   )
@@ -1299,7 +1318,7 @@ Serve.prototype.renderThreadPaginated = function (opts, feedId, q) {
       function onFirst(msg, cb) {
         var num = feedId ? msg.value.sequence :
           opts.sortByTimestamp ? msg.value.timestamp :
-	  msg.timestamp || msg.ts
+          msg.timestamp || msg.ts
         if (q.forwards) {
           cb(null, links({
             lt: num,
@@ -1327,7 +1346,7 @@ Serve.prototype.renderThreadPaginated = function (opts, feedId, q) {
       function onLast(msg, cb) {
         var num = feedId ? msg.value.sequence :
           opts.sortByTimestamp ? msg.value.timestamp :
-	  msg.timestamp || msg.ts
+          msg.timestamp || msg.ts
         if (q.forwards) {
           cb(null, links({
             lt: null,
@@ -1570,8 +1589,8 @@ Serve.prototype.friendInfo = function (id, myId) {
     this.app.render.friendsList(),
     pull.map(function (html) {
       if (!first) {
-	first = true
-	return 'followed by your friends: ' + html
+        first = true
+        return 'followed by your friends: ' + html
       }
       return html
     })
@@ -1623,15 +1642,15 @@ Serve.prototype.wrapUserFeed = function (isScrolled, id) {
           )
         ]),
         isScrolled || id === myId ? '' : [
-	  ph('tr', [
-	    ph('td'),
-	    ph('td', {class: 'follow-info'}, self.followInfo(id, myId))
-	  ]),
-	  ph('tr', [
-	    ph('td'),
-	    ph('td', self.friendInfo(id, myId))
-	  ])
-	]
+          ph('tr', [
+            ph('td'),
+            ph('td', {class: 'follow-info'}, self.followInfo(id, myId))
+          ]),
+          ph('tr', [
+            ph('td'),
+            ph('td', self.friendInfo(id, myId))
+          ])
+        ]
       ])),
       thread
     ])
@@ -1646,6 +1665,8 @@ Serve.prototype.git = function (url) {
     case 'tree': return this.gitTree(m[2])
     case 'blob': return this.gitBlob(m[2])
     case 'raw': return this.gitRaw(m[2])
+    case 'diff': return this.gitDiff(m[2])
+    case 'line-comment': return this.gitLineComment(m[2])
     default: return this.respond(404, 'Not found')
   }
 }
@@ -1780,13 +1801,29 @@ Serve.prototype.gitCommit = function (rev) {
               pull.map(function (file) {
                 return ph('tr', [
                   ph('td', ph('code', u.escapeHTML(file.name))),
-                  // ph('td', ph('code', u.escapeHTML(JSON.stringify(file.msg)))),
                   ph('td', file.deleted ? 'deleted'
-                         : file.created ? 'created'
-                         : file.hash ? 'changed'
+                         : file.created ?
+                    ph('a', {href:
+                      self.app.render.toUrl('/git/blob/'
+                        + (file.hash[1] || file.hash[0])
+                        + '?msg=' + encodeURIComponent(obj.msg.key))
+                    }, 'created')
+                         : file.hash ?
+                    ph('a', {href:
+                      self.app.render.toUrl('/git/diff/'
+                        + file.hash[0] + '..' + file.hash[1]
+                        + '?msg=' + encodeURIComponent(obj.msg.key))
+                        + '&commit=' + rev
+                        + '&path=' + encodeURIComponent(file.name)
+                    }, 'changed')
                          : file.mode ? 'mode changed'
                          : JSON.stringify(file))
                 ])
+              }),
+              Catch(function (err) {
+                if (err && err.name === 'ObjectNotFoundError') return
+                if (err && err.name === 'BlobNotFoundError') return self.askWantBlobsForm(err.links)
+                  return false
               })
             ))
           ]
@@ -1908,23 +1945,8 @@ Serve.prototype.gitTree = function (rev) {
         ]),
         missingBlobs ? self.askWantBlobsForm(missingBlobs) : ph('table', [
           pull(
-            self.app.git.readTree(obj),
-            paramap(function (file, cb) {
-              self.app.git.getObjectMsg({
-                obj: file.hash,
-                headMsgId: obj.msg.key,
-              }, function (err, msg) {
-                if (err && err.name === 'ObjectNotFoundError') return cb(null, file)
-                if (err && err.name === 'BlobNotFoundError') return cb(null, {missingBlobs: err.links})
-                if (err) return cb(err)
-                file.msg = msg
-                cb(null, file)
-              })
-            }, 8),
+            self.app.git.readTreeFull(obj),
             pull.map(function (item) {
-	      if (item.missingBlobs) {
-		return self.askWantBlobsForm(item.missingBlobs)
-	      }
               if (!item.msg) return ph('tr', [
                 ph('td',
                   u.escapeHTML(item.name) + (item.type === 'tree' ? '/' : '')),
@@ -1949,6 +1971,11 @@ Serve.prototype.gitTree = function (rev) {
                   }, htime(fileDate))
                 ),
               ])
+            }),
+            Catch(function (err) {
+              if (err && err.name === 'ObjectNotFoundError') return
+              if (err && err.name === 'BlobNotFoundError') return self.askWantBlobsForm(err.links)
+              return false
             })
           )
         ]),
@@ -2006,6 +2033,7 @@ Serve.prototype.gitBlob = function (rev) {
           missingBlobs ? self.askWantBlobsForm(missingBlobs) : pull(
             self.app.git.readObject(obj),
             self.wrapBinary({
+              obj: obj,
               rawUrl: self.app.render.toUrl('/git/raw/' + rev
                 + '?msg=' + encodeURIComponent(msg.key)),
               ext: self.query.ext
@@ -2019,6 +2047,295 @@ Serve.prototype.gitBlob = function (rev) {
   })
 }
 
+Serve.prototype.gitDiff = function (revs) {
+  var self = this
+  var parts = revs.split('..')
+  if (parts.length !== 2) return pull(
+    ph('div.error', 'revs should be <rev1>..<rev2>'),
+    self.wrapPage('git diff'),
+    self.respondSink(400)
+  )
+  var rev1 = parts[0]
+  var rev2 = parts[1]
+  if (!/[0-9a-f]{24}/.test(rev1)) return pull(
+    ph('div.error', 'rev 1 is not a git object id'),
+    self.wrapPage('git diff'),
+    self.respondSink(400)
+  )
+  if (!/[0-9a-f]{24}/.test(rev2)) return pull(
+    ph('div.error', 'rev 2 is not a git object id'),
+    self.wrapPage('git diff'),
+    self.respondSink(400)
+  )
+
+  if (!u.isRef(self.query.msg)) return pull(
+    ph('div.error', 'missing message id'),
+    self.wrapPage('git diff'),
+    self.respondSink(400)
+  )
+
+  var done = multicb({pluck: 1, spread: true})
+  // the msg qs param should point to the message for rev2 object. the msg for
+  // rev1 object we will have to look up.
+  self.app.git.getObjectMsg({
+    obj: rev1,
+    headMsgId: self.query.msg,
+    type: 'blob',
+  }, done())
+  self.getMsgDecryptedMaybeOoo(self.query.msg, done())
+  done(function (err, msg1, msg2) {
+    if (err) return pull(
+      pull.once(u.renderError(err).outerHTML),
+      self.wrapPage('git diff ' + revs),
+      self.respondSink(400)
+    )
+    var msg1Date = new Date(msg1.value.timestamp)
+    var msg2Date = new Date(msg2.value.timestamp)
+    var revsShort = rev1.substr(0, 8) + '..' + rev2.substr(0, 8)
+    pull(
+      ph('section', [
+        ph('h3', ph('a', {href: ''}, revsShort)),
+        ph('div', [
+          ph('a', {
+            href: self.app.render.toUrl('/git/blob/' + rev1 + '?msg=' + encodeURIComponent(msg1.key))
+          }, rev1), ' ',
+          self.phIdLink(msg1.value.author), ' ',
+          ph('a', {
+            href: self.app.render.toUrl(msg1.key),
+            title: msg1Date.toLocaleString(),
+          }, htime(msg1Date))
+        ]),
+        ph('div', [
+          ph('a', {
+            href: self.app.render.toUrl('/git/blob/' + rev2 + '?msg=' + encodeURIComponent(msg2.key))
+          }, rev2), ' ',
+          self.phIdLink(msg2.value.author), ' ',
+          ph('a', {
+            href: self.app.render.toUrl(msg2.key),
+            title: msg2Date.toLocaleString(),
+          }, htime(msg2Date))
+        ]),
+        u.readNext(function (cb) {
+          var done = multicb({pluck: 1, spread: true})
+          self.app.git.openObject({
+            obj: rev1,
+            msg: msg1.key,
+          }, done())
+          self.app.git.openObject({
+            obj: rev2,
+            msg: msg2.key,
+          }, done())
+          /*
+          self.app.git.guessCommitAndPath({
+            obj: rev2,
+            msg: msg2.key,
+          }, done())
+          */
+          done(function (err, obj1, obj2/*, info2*/) {
+            if (err && err.name === 'BlobNotFoundError')
+              return cb(null, self.askWantBlobsForm(err.links))
+            if (err) return cb(err)
+
+            var done = multicb({pluck: 1, spread: true})
+            pull.collect(done())(self.app.git.readObject(obj1))
+            pull.collect(done())(self.app.git.readObject(obj2))
+            self.app.getLineComments({obj: obj2, hash: rev2}, done())
+            done(function (err, bufs1, bufs2, lineComments) {
+              if (err) return cb(err)
+              var str1 = Buffer.concat(bufs1, obj1.length).toString('utf8')
+              var str2 = Buffer.concat(bufs2, obj2.length).toString('utf8')
+              var diff = Diff.structuredPatch('', '', str1, str2)
+              cb(null, self.gitDiffTable(diff, lineComments, {
+                obj: obj2,
+                hash: rev2,
+                commit: self.query.commit, // info2.commit,
+                path: self.query.path, // info2.path,
+              }))
+            })
+          })
+        })
+      ]),
+      self.wrapPage('git diff'),
+      self.respondSink(200)
+    )
+  })
+}
+
+Serve.prototype.gitDiffTable = function (diff, lineComments, lineCommentInfo) {
+  var updateMsg = lineCommentInfo.obj.msg
+  var self = this
+  return pull(
+    ph('table', [
+      pull(
+        pull.values(diff.hunks),
+        pull.map(function (hunk) {
+          var oldLine = hunk.oldStart
+          var newLine = hunk.newStart
+          return [
+            ph('tr', [
+              ph('td', {colspan: 3}),
+              ph('td', ph('pre',
+                '@@ -' + oldLine + ',' + hunk.oldLines + ' ' +
+                '+' + newLine + ',' + hunk.newLines + ' @@'))
+            ]),
+            pull(
+              pull.values(hunk.lines),
+              pull.map(function (line) {
+                var s = line[0]
+                if (s == '\\') return
+                var html = self.app.render.highlight(line)
+                var lineNums = [s == '+' ? '' : oldLine++, s == '-' ? '' : newLine++]
+                var hash = lineCommentInfo.hash
+                var newLineNum = lineNums[lineNums.length-1]
+                var id = hash + '-' + (newLineNum || (lineNums[0] + '-'))
+                var idEnc = encodeURIComponent(id)
+                var allowComment = s !== '-'
+                  && self.query.commit && self.query.path
+                return [
+                  ph('tr', {
+                    class: s == '+' ? 'diff-new' : s == '-' ? 'diff-old' : ''
+                  }, [
+                    lineNums.map(function (num, i) {
+                      return ph('td', [
+                        ph('a', {
+                          name: i === 0 ? idEnc : undefined,
+                          href: '#' + idEnc
+                        }, String(num))
+                      ])
+                    }),
+                    ph('td',
+                      allowComment ? ph('a', {
+                        href: '?msg=' +
+                          encodeURIComponent(self.query.msg)
+                          + '&comment=' + idEnc
+                          + '&commit=' + encodeURIComponent(self.query.commit)
+                          + '&path=' + encodeURIComponent(self.query.path)
+                          + '#' + idEnc
+                      }, '…') : ''
+                    ),
+                    ph('td', ph('pre', u.escapeHTML(html)))
+                  ]),
+                  (lineComments[newLineNum] ?
+                    ph('tr',
+                      ph('td', {colspan: 4},
+                        self.renderLineCommentThread(lineComments[newLineNum], id)
+                      )
+                    )
+                  : newLineNum && lineCommentInfo && self.query.comment === id ?
+                    ph('tr',
+                      ph('td', {colspan: 4},
+                        self.renderLineCommentForm({
+                          id: id,
+                          line: newLineNum,
+                          updateId: updateMsg.key,
+                          repoId: updateMsg.value.content.repo,
+                          commitId: lineCommentInfo.commit,
+                          filePath: lineCommentInfo.path,
+                        })
+                      )
+                    )
+                  : '')
+                ]
+              })
+            )
+          ]
+        })
+      )
+    ])
+  )
+}
+
+Serve.prototype.renderLineCommentThread = function (lineComment, id) {
+  return this.streamThreadWithComposer({
+    root: lineComment.msg.key,
+    id: id,
+    placeholder: 'reply to line comment thread'
+  })
+}
+
+Serve.prototype.renderLineCommentForm = function (opts) {
+  return [
+    this.phComposer({
+      placeholder: 'comment on this line',
+      id: opts.id,
+      lineComment: opts
+    })
+  ]
+}
+
+// return a composer, pull-hyperscript style
+Serve.prototype.phComposer = function (opts) {
+  var self = this
+  return u.readNext(function (cb) {
+    self.composer(opts, function (err, composer) {
+      if (err) return cb(err)
+      cb(null, pull.once(composer.outerHTML))
+    })
+  })
+}
+
+Serve.prototype.gitLineComment = function (path) {
+  var self = this
+  var id
+  try {
+    id = decodeURIComponent(String(path))
+    if (id[0] === '%') {
+      return self.getMsgDecryptedMaybeOoo(id, gotMsg)
+    } else {
+      msg = JSON.parse(id)
+    }
+  } catch(e) {
+    return gotMsg(e)
+  }
+  gotMsg(null, msg)
+  function gotMsg(err, msg) {
+    if (err) return pull(
+      pull.once(u.renderError(err).outerHTML),
+      self.respondSink(400, {'Content-Type': ctype('html')})
+    )
+    var c = msg && msg.value && msg.value.content
+    if (!c) return pull(
+      pull.once('Missing message ' + id),
+      self.respondSink(500, {'Content-Type': ctype('html')})
+    )
+    self.app.git.diffFile({
+      msg: c.updateId,
+      commit: c.commitId,
+      path: c.filePath,
+    }, function (err, file) {
+      if (err && err.name === 'BlobNotFoundError')
+        return self.askWantBlobs(err.links)
+      if (err) return pull(
+        pull.once(err.stack),
+        self.respondSink(400, {'Content-Type': 'text/plain'})
+      )
+      var path
+      if (file.created) {
+        path = '/git/blob/' + file.hash[1]
+          + '?msg=' + encodeURIComponent(c.updateId)
+          + '&commit=' + c.commitId
+          + '&path=' + encodeURIComponent(c.filePath)
+          + '#' + file.hash[1] + '-' + c.line
+      } else {
+        path = '/git/diff/' + file.hash[0] + '..' + file.hash[1]
+          + '?msg=' + encodeURIComponent(c.updateId)
+          + '&commit=' + c.commitId
+          + '&path=' + encodeURIComponent(c.filePath)
+          + '#' + file.hash[1] + '-' + c.line
+      }
+      var url = self.app.render.toUrl(path)
+      /*
+      return pull(
+        ph('a', {href: url}, path),
+        self.wrapPage(id),
+        self.respondSink(200)
+      )
+      */
+      self.redirect(url)
+    })
+  }
+}
+
 Serve.prototype.gitObjectLinks = function (headMsgId, type) {
   var self = this
   return paramap(function (id, cb) {
@@ -2310,6 +2627,7 @@ Serve.prototype.zip = function (url) {
 Serve.prototype.wrapBinary = function (opts) {
   var self = this
   var ext = opts.ext
+  var hash = opts.obj.hash
   return function (read) {
     var readRendered, type
     read = ident(function (_ext) {
@@ -2336,9 +2654,76 @@ Serve.prototype.wrapBinary = function (opts) {
         src: opts.rawUrl
       })
     }
-    return ph('pre', pull.map(function (buf) {
-      return self.app.render.highlight(buf.toString('utf8'), ext)
-    })(read))
+    if (type === 'text/markdown') {
+      // TODO: rewrite links to files/images to be correct
+      return ph('blockquote', u.readNext(function (cb) {
+        pull.collect(function (err, bufs) {
+          if (err) return cb(pull.error(err))
+          var text = Buffer.concat(bufs).toString('utf8')
+          return cb(null, pull.once(self.app.render.markdown(text)))
+        })(read)
+      }))
+    }
+    var i = 0
+    var updateMsg = opts.obj.msg
+    var commitId = self.query.commit
+    var filePath = self.query.path
+    var lineComments = opts.lineComments || {}
+    return u.readNext(function (cb) {
+      if (commitId && filePath) {
+        self.app.getLineComments({
+          obj: opts.obj,
+          hash: hash,
+        }, gotLineComments)
+      } else {
+        gotLineComments(null, {})
+      }
+      function gotLineComments(err, lineComments) {
+        if (err) return cb(err)
+        cb(null, ph('table',
+          pull(
+            read,
+            utf8(),
+            split(),
+            pull.map(function (line) {
+              var lineNum = i++
+              var id = hash + '-' + lineNum
+              var idEnc = encodeURIComponent(id)
+              return [
+                ph('tr', [
+                  ph('td', ph('a', {
+                    name: id,
+                    href: '?msg=' + encodeURIComponent(self.query.msg)
+                      + '&commit=' + encodeURIComponent(self.query.commit)
+                      + '&path=' + encodeURIComponent(self.query.path)
+                      + '&comment=' + idEnc
+                      + '#' + idEnc
+                  }, String(lineNum))),
+                  ph('td', ph('pre', self.app.render.highlight(line, ext)))
+                ]),
+                lineComments[lineNum] ? ph('tr',
+                  ph('td', {colspan: 4},
+                    self.renderLineCommentThread(lineComments[lineNum], id)
+                  )
+                ) : '',
+                self.query.comment === id ? ph('tr',
+                  ph('td', {colspan: 4},
+                    self.renderLineCommentForm({
+                      id: id,
+                      line: lineNum,
+                      updateId: updateMsg.key,
+                      repoId: updateMsg.value.content.repo,
+                      commitId: commitId,
+                      filePath: filePath,
+                    })
+                  )
+                ) : ''
+              ]
+            })
+          )
+        ))
+      }
+    })
   }
 }
 
@@ -2409,7 +2794,8 @@ Serve.prototype.wrapThread = function (opts) {
     self.app.render.prepareLinks(opts.recps, function (err, recps) {
       if (err) return cb(er)
       self.composer({
-        placeholder: recps ? 'private reply' : 'reply',
+        placeholder: opts.placeholder
+          || (recps ? 'private reply' : 'reply'),
         id: 'reply',
         root: opts.root,
         post: opts.post,
@@ -2552,6 +2938,11 @@ Serve.prototype.composer = function (opts, cb) {
   var data = self.data
   var myId = self.app.sbot.id
 
+  if (opts.id && data.composer_id && opts.id !== data.composer_id) {
+    // don't share data between multiple composers
+    data = {}
+  }
+
   if (!data.text && self.query.text) data.text = self.query.text
   if (!data.action && self.query.action) data.action = self.query.action
 
@@ -2645,6 +3036,7 @@ Serve.prototype.composer = function (opts, cb) {
       enctype: 'multipart/form-data'},
       h('input', {type: 'hidden', name: 'blobs',
         value: JSON.stringify(blobs)}),
+      h('input', {type: 'hidden', name: 'composer_id', value: opts.id}),
       opts.recps ? self.app.render.privateLine(opts.recps, done()) :
       opts.private ? h('div', h('input.recps-input', {name: 'recps',
         value: data.recps || '', placeholder: 'recipient ids'})) : '',
@@ -2712,6 +3104,14 @@ Serve.prototype.composer = function (opts, cb) {
       type: 'post',
       text: String(data.text).replace(/\r\n/g, '\n'),
     }
+    if (opts.lineComment) {
+      content.type = 'line-comment'
+      content.updateId = opts.lineComment.updateId
+      content.repo = opts.lineComment.repoId
+      content.commitId = opts.lineComment.commitId
+      content.filePath = opts.lineComment.filePath
+      content.line = opts.lineComment.line
+    }
     var mentions = ssbMentions(data.text, {bareFeedNames: true, emoji: true})
       .filter(function (mention) {
         if (mention.emoji) {
@@ -2815,15 +3215,15 @@ Serve.prototype.composer = function (opts, cb) {
       })
 
       var draftMsg = {
-	key: '%0000000000000000000000000000000000000000000=.sha256',
-	value: {
-	  previous: '%0000000000000000000000000000000000000000000=.sha256',
-	  author: '@0000000000000000000000000000000000000000000=.ed25519',
-	  sequence: 1000,
-	  timestamp: 1000000000000,
-	  hash: 'sha256',
-	  content: content
-	}
+        key: '%0000000000000000000000000000000000000000000=.sha256',
+        value: {
+          previous: '%0000000000000000000000000000000000000000000=.sha256',
+          author: '@0000000000000000000000000000000000000000000=.ed25519',
+          sequence: 1000,
+          timestamp: 1000000000000,
+          hash: 'sha256',
+          content: content
+        }
       }
       var estSize = JSON.stringify(draftMsg, null, 2).length
       sizeEl.innerHTML = self.app.render.formatSize(estSize)
@@ -2838,9 +3238,9 @@ Serve.prototype.composer = function (opts, cb) {
         pull.once(msg),
         self.app.unboxMessages(),
         self.app.render.renderFeeds({
-	  raw: raw,
-	  filter: self.query.filter,
-	}),
+          raw: raw,
+          filter: self.query.filter,
+        }),
         pull.drain(function (el) {
           msgContainer.appendChild(h('tbody', el))
         }, cb)
diff --git a/package-lock.json b/package-lock.json
index 0f5d62f..905c326 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -180,6 +180,11 @@
         "streamsearch": "0.1.2"
       }
     },
+    "diff": {
+      "version": "3.3.1",
+      "resolved": "http://localhost:8989/blobs/get/&+6G9mvp4Q/5bujMKlbFdbrub2IXMPleXIqTqyyvY5Ww=.sha256",
+      "integrity": "sha1-qoVnpu7QPFMfyJ0/cRzQ5SWd7HU="
+    },
     "ed2curve": {
       "version": "0.1.4",
       "resolved": "http://localhost:8989/blobs/get/&X6VtEiGqSVFiIHAZAXFZXB5q9iUd3gULIU9c0xyynNo=.sha256",
@@ -492,6 +497,7 @@
         "readable-stream": {
           "version": "1.0.34",
           "resolved": "http://localhost:8989/blobs/get/&0QEMlyAUePLZCW/tXOEhdYfVI4R19FBv4JyHzdW8VqY=.sha256",
+          "integrity": "sha1-Elgg40vIQtLyqq+v5MKRbuMsFXw=",
           "requires": {
             "core-util-is": "http://localhost:8989/blobs/get/&pKRNq2V57ePgat5Y0m+P1kLq4JFT/VnGCPy3lRpJk5g=.sha256",
             "inherits": "2.0.3",
@@ -772,17 +778,15 @@
       "resolved": "http://localhost:8989/blobs/get/&+uVE8RHNwJIJa68sQGICGbxnCTCOdLLhSt/Pb4NmgL0=.sha256",
       "integrity": "sha256-+uVE8RHNwJIJa68sQGICGbxnCTCOdLLhSt/Pb4NmgL0="
     },
+    "pull-catch": {
+      "version": "1.0.0",
+      "resolved": "http://localhost:8989/blobs/get/&K8t9klRhYJkdveaxSpBMFwzMtmNyLwNRTQUeCVnUvYU=.sha256",
+      "integrity": "sha256-K8t9klRhYJkdveaxSpBMFwzMtmNyLwNRTQUeCVnUvYU="
+    },
     "pull-defer": {
       "version": "http://localhost:8989/blobs/get/&mDI2o/JC9yvFOVbeAhDN+hwTm7cK+dBwISYO49EMY24=.sha256",
       "integrity": "sha1-CIew/7MK8ypW2+z6csFnInHwexM="
     },
-    "pull-git-packidx-parser": {
-      "version": "http://localhost:8989/blobs/get/&ou0MPQZabBgzrHDu54jzLU3Sc6Rf5a/lost0whPQUJ0=.sha256",
-      "integrity": "sha1-LYvwr+SCSJfuA4QL/k9ahq/syiE=",
-      "requires": {
-        "pull-stream": "3.6.1"
-      }
-    },
     "pull-goodbye": {
       "version": "0.0.2",
       "resolved": "http://localhost:8989/blobs/get/&MQhN9Pp3BYaj0TzxK39JfAK7CjVceg1EPfNhhFnZ9sU=.sha256",
@@ -842,14 +846,6 @@
         }
       }
     },
-    "pull-kvdiff": {
-      "version": "0.0.1",
-      "resolved": "http://localhost:8989/blobs/get/&xxfT88LrbK4FSIhpaNmIAt4jzsaBgVugeaDPVwC1gCU=.sha256",
-      "integrity": "sha256-xxfT88LrbK4FSIhpaNmIAt4jzsaBgVugeaDPVwC1gCU=",
-      "requires": {
-        "multicb": "1.2.2"
-      }
-    },
     "pull-many": {
       "version": "http://localhost:8989/blobs/get/&wBHfPheBEjwjjkNoeM5mWtU/tYDs8+xnt5w6C1+EK3g=.sha256",
       "integrity": "sha1-Pa3ZttFWxUVyG9qNAAPdjqoGKT4=",
@@ -884,6 +880,14 @@
       "resolved": "http://localhost:8989/blobs/get/&fFOPAd5Js7mJkEU4XHeJ6vE6H7nsTOegHpjY0hpTu00=.sha256",
       "integrity": "sha256-fFOPAd5Js7mJkEU4XHeJ6vE6H7nsTOegHpjY0hpTu00="
     },
+    "pull-split": {
+      "version": "0.2.0",
+      "resolved": "http://localhost:8989/blobs/get/&OWAh7XbI03yih8UH5Vu0qrYM6TGx0q8uah06dm22CJo=.sha256",
+      "integrity": "sha256-OWAh7XbI03yih8UH5Vu0qrYM6TGx0q8uah06dm22CJo=",
+      "requires": {
+        "pull-through": "1.0.18"
+      }
+    },
     "pull-stream": {
       "version": "3.6.1",
       "resolved": "http://localhost:8989/blobs/get/&xEhoJll+9Z5EYr7s7MUgCbBhdF1nekcqnIdIKV4z2SU=.sha256",
@@ -904,6 +908,11 @@
         }
       }
     },
+    "pull-utf8-decoder": {
+      "version": "1.0.2",
+      "resolved": "http://localhost:8989/blobs/get/&JHBdLm6x7Rsu08/eLVWYKq+YpGna4xnvqM44ucX2tpk=.sha256",
+      "integrity": "sha256-JHBdLm6x7Rsu08/eLVWYKq+YpGna4xnvqM44ucX2tpk="
+    },
     "pull-ws": {
       "version": "3.3.0",
       "resolved": "http://localhost:8989/blobs/get/&xe26a32xW10OFqKs+xdyUTSobJPCAGdnv7yIAjoqmlk=.sha256",
@@ -928,6 +937,7 @@
         "readable-stream": {
           "version": "1.0.34",
           "resolved": "http://localhost:8989/blobs/get/&0QEMlyAUePLZCW/tXOEhdYfVI4R19FBv4JyHzdW8VqY=.sha256",
+          "integrity": "sha1-Elgg40vIQtLyqq+v5MKRbuMsFXw=",
           "requires": {
             "core-util-is": "http://localhost:8989/blobs/get/&pKRNq2V57ePgat5Y0m+P1kLq4JFT/VnGCPy3lRpJk5g=.sha256",
             "inherits": "2.0.3",
@@ -1069,6 +1079,7 @@
         "readable-stream": {
           "version": "1.0.34",
           "resolved": "http://localhost:8989/blobs/get/&0QEMlyAUePLZCW/tXOEhdYfVI4R19FBv4JyHzdW8VqY=.sha256",
+          "integrity": "sha1-Elgg40vIQtLyqq+v5MKRbuMsFXw=",
           "requires": {
             "core-util-is": "http://localhost:8989/blobs/get/&pKRNq2V57ePgat5Y0m+P1kLq4JFT/VnGCPy3lRpJk5g=.sha256",
             "inherits": "2.0.3",
@@ -1206,6 +1217,30 @@
       "version": "http://localhost:8989/blobs/get/&5yyYBZpB4w+X6kW42KMh43Xz9KP3XW79mYOj40/CHA4=.sha256",
       "integrity": "sha1-Fg4kETeCqcpegGByqnpl58hl2/I="
     },
+    "ssb-mentions": {
+      "version": "http://localhost:8989/blobs/get/&GjuxknqKwJqHznKueFNCyIh52v1woz5PB41vqmoHfyM=.sha256",
+      "integrity": "sha1-AMd4SslTCsJi2h5902MlCCA1UEY=",
+      "requires": {
+        "ssb-marked": "http://localhost:8989/blobs/get/&5yyYBZpB4w+X6kW42KMh43Xz9KP3XW79mYOj40/CHA4=.sha256",
+        "ssb-ref": "2.7.1"
+      },
+      "dependencies": {
+        "is-valid-domain": {
+          "version": "0.0.2",
+          "resolved": "http://localhost:8989/blobs/get/&phjiap+k1lGC5LPVba/w4Caomw5o0NQp2Hol+u/YAzE=.sha256",
+          "integrity": "sha1-PnqUI/98Oy/hFmOvvW04N6JR+3c="
+        },
+        "ssb-ref": {
+          "version": "2.7.1",
+          "resolved": "http://localhost:8989/blobs/get/&wLimOD3785KVj7kBIAbjN6GH8EMhKRkcZSPrEMhdhks=.sha256",
+          "integrity": "sha1-XU7/xUXsD/1/wVuieCmmQLiir7o=",
+          "requires": {
+            "ip": "1.1.5",
+            "is-valid-domain": "0.0.2"
+          }
+        }
+      }
+    },
     "ssb-ref": {
       "version": "http://localhost:8989/blobs/get/&wLimOD3785KVj7kBIAbjN6GH8EMhKRkcZSPrEMhdhks=.sha256",
       "integrity": "sha1-XU7/xUXsD/1/wVuieCmmQLiir7o=",
@@ -1337,6 +1372,7 @@
         "readable-stream": {
           "version": "1.0.34",
           "resolved": "http://localhost:8989/blobs/get/&0QEMlyAUePLZCW/tXOEhdYfVI4R19FBv4JyHzdW8VqY=.sha256",
+          "integrity": "sha1-Elgg40vIQtLyqq+v5MKRbuMsFXw=",
           "requires": {
             "core-util-is": "http://localhost:8989/blobs/get/&pKRNq2V57ePgat5Y0m+P1kLq4JFT/VnGCPy3lRpJk5g=.sha256",
             "inherits": "2.0.3",
diff --git a/package.json b/package.json
index d4f48d7..37d3ca4 100644
--- a/package.json
+++ b/package.json
@@ -6,6 +6,7 @@
     "asyncmemo": "^1.1.0",
     "base64-url": "^2.0.0",
     "busboy": "^0.2.14",
+    "diff": "^3.3.1",
     "emoji-named-characters": "^1.0.2",
     "emoji-server": "^1.0.0",
     "hashlru": "^2.1.0",
@@ -13,21 +14,22 @@
     "human-time": "^0.0.1",
     "hyperscript": "^2.0.2",
     "jpeg-autorotate": "^3.0.0",
-    "looper": "^4.0.0",
     "mime-types": "^2.1.12",
     "multicb": "^1.2.1",
     "pull-box-stream": "^1.0.12",
     "pull-cat": "^1.1.11",
-    "pull-git-packidx-parser": "^1.0.0",
+    "pull-catch": "^1.0.0",
     "pull-hyperscript": "^0.2.2",
     "pull-identify-filetype": "^1.1.0",
-    "pull-kvdiff": "^0.0.1",
     "pull-paginate": "^1.0.0",
     "pull-paramap": "^1.2.1",
     "pull-reader": "^1.2.9",
+    "pull-split": "^0.2.0",
     "pull-stream": "^3.5.0",
+    "pull-utf8-decoder": "^1.0.2",
     "ssb-client": "http://localhost:8989/blobs/get/&EAaUpI+wrJM5/ly1RqZW0GAEF4PmCAmABBj7e6UIrL0=.sha256",
     "ssb-contact": "^1.2.0",
+    "ssb-git": "^0.6.0",
     "ssb-marked": "^0.7.1",
     "ssb-mentions": "http://localhost:8989/blobs/get/&GjuxknqKwJqHznKueFNCyIh52v1woz5PB41vqmoHfyM=.sha256",
     "ssb-sort": "^1.0.0",
diff --git a/static/styles.css b/static/styles.css
index c26cf59..b22074f 100644
--- a/static/styles.css
+++ b/static/styles.css
@@ -193,3 +193,6 @@ table.ssb-object td {
 .chess-square-dark {
   background-color: #ccc;
 }
+
+.diff-old { background-color: #ffe2dd; }
+.diff-new { background-color: #d1ffd6; }