diff --git a/tests/drawdag.py b/tests/drawdag.py
--- a/tests/drawdag.py
+++ b/tests/drawdag.py
@@ -84,6 +84,7 @@ from __future__ import absolute_import, 
 
 import collections
 import itertools
+import re
 
 from mercurial.i18n import _
 from mercurial import (
@@ -275,6 +276,12 @@ def _walkgraph(edges):
                 if leaf in v:
                     v.remove(leaf)
 
+def _getcomments(text):
+    for line in text.splitlines():
+        if ' # ' not in line:
+            continue
+        yield line.split(' # ', 1)[1].split(' # ')[0].strip()
+
 @command('debugdrawdag', [])
 def debugdrawdag(ui, repo, **opts):
     """read an ASCII graph from stdin and create changesets
@@ -301,6 +308,13 @@ def debugdrawdag(ui, repo, **opts):
             raise error.Abort(_('%s: too many parents: %s')
                               % (k, ' '.join(v)))
 
+    # parse comments to get extra file content instructions
+    files = collections.defaultdict(dict) # {(name, path): content}
+    comments = list(_getcomments(text))
+    filere = re.compile(r'^(\w+)/([\w/]+)\s*=\s*(.*)$', re.M)
+    for name, path, content in filere.findall('\n'.join(comments)):
+        files[name][path] = content.replace(r'\n', '\n')
+
     committed = {None: node.nullid}  # {name: node}
 
     # for leaf nodes, try to find existing nodes in repo
@@ -326,6 +340,9 @@ def debugdrawdag(ui, repo, **opts):
         else:
             # If it's not a merge, add a single file
             added[name] = name
+        # add extra file contents in comments
+        for path, content in files.get(name, {}).items():
+            added[path] = content
         ctx = simplecommitctx(repo, name, pctxs, added)
         n = ctx.commit()
         committed[name] = n
@@ -335,12 +352,8 @@ def debugdrawdag(ui, repo, **opts):
     # handle special comments
     with repo.wlock(), repo.lock(), repo.transaction('drawdag'):
         getctx = lambda x: repo.unfiltered()[committed[x.strip()]]
-        for line in text.splitlines():
-            if ' # ' not in line:
-                continue
-
+        for comment in comments:
             rels = [] # obsolete relationships
-            comment = line.split(' # ', 1)[1].split(' # ')[0].strip()
             args = comment.split(':', 1)
             if len(args) <= 1:
                 continue
diff --git a/tests/test-drawdag.t b/tests/test-drawdag.t
--- a/tests/test-drawdag.t
+++ b/tests/test-drawdag.t
@@ -232,3 +232,41 @@ Create obsmarkers via comments
   be0ef73c17ade3fc89dc41701eb9fc3a91b58282 575c4b5ec114d64b681d33f8792853568bfb2b2c 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
   64a8289d249234b9886244d379f15e6b650b28e3 0 {7fb047a69f220c21711122dfd94305a9efb60cba} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
   58e6b987bf7045fcd9c54f496396ca1d1fc81047 0 {575c4b5ec114d64b681d33f8792853568bfb2b2c} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
+
+Change file contents via comments
+
+  $ reinit
+  $ hg debugdrawdag <<'EOS'
+  > C       # A/dir1/a = 1\n2
+  > |\      # B/dir2/b = 34
+  > A B     # C/dir1/c = 5
+  >         # C/dir2/c = 6
+  >         # C/A = a
+  >         # C/B = b
+  > EOS
+
+  $ hg log -G -T '{desc} {files}'
+  o    C A B dir1/c dir2/c
+  |\
+  | o  B B dir2/b
+  |
+  o  A A dir1/a
+  
+  $ for f in `hg files -r C`; do
+  >   echo FILE "$f"
+  >   hg cat -r C "$f"
+  >   echo
+  > done
+  FILE A
+  a
+  FILE B
+  b
+  FILE dir1/a
+  1
+  2
+  FILE dir1/c
+  5
+  FILE dir2/b
+  34
+  FILE dir2/c
+  6