subrepo: compare svn subrepo state to last committed revision

A subversion project revisions are a subset of the repository revisions, you
can ask subversion to update a working directory from one revision to another
without changing anything. Unfortunately, Mercurial will think the
subrepository has changed and will commit it again. To avoid useless commits,
we compare the subrepository state to its actual "parent" revision. To ensure
ascending compatibility with existing subrepositories which might reference
fake revisions, we also keep comparing with the subrepo working directory
revision.

NOTE: not sure if this should go in stable or not.

mercurial/subrepo.py

@@ -499,13 +499,23 b' class svnsubrepo(abstractsubrepo):'
             raise util.Abort(stderr)
         return stdout
 
-    def _wcrev(self):
+    def _wcrevs(self):
+        # Get the working directory revision as well as the last
+        # commit revision so we can compare the subrepo state with
+        # both. We used to store the working directory one.
         output = self._svncommand(['info', '--xml'])
         doc = xml.dom.minidom.parseString(output)
         entries = doc.getElementsByTagName('entry')
-        if not entries:
-            return '0'
-        return str(entries[0].getAttribute('revision')) or '0'
+        lastrev, rev = '0', '0'
+        if entries:
+            rev = str(entries[0].getAttribute('revision')) or '0'
+            commits = entries[0].getElementsByTagName('commit')
+            if commits:
+                lastrev = str(commits[0].getAttribute('revision')) or '0'
+        return (lastrev, rev)
+
+    def _wcrev(self):
+        return self._wcrevs()[0]
 
     def _wcchanged(self):
         """Return (changes, extchanges) where changes is True
@@ -534,7 +544,7 b' class svnsubrepo(abstractsubrepo):'
         return bool(changes), False
 
     def dirty(self):
-        if self._wcrev() == self._state[1] and not self._wcchanged()[0]:
+        if self._state[1] in self._wcrevs() and not self._wcchanged()[0]:
             return False
         return True
 

tests/test-subrepo-svn.t

@@ -123,6 +123,25 b' change file in svn and hg, commit'
    source   file://*/svn-repo/src (glob)
    revision 2
 
+add an unrelated revision in svn and update the subrepo to without
+bringing any changes.
+
+  $ svn mkdir --parents "$SVNREPO/unrelated" -m 'create unrelated'
+  
+  Committed revision 4.
+  $ svn up s
+  
+  Fetching external item into 's/externals'
+  External at revision 1.
+  
+  At revision 4.
+  $ hg sum
+  parent: 2:* tip (glob)
+   Message!
+  branch: default
+  commit: (clean)
+  update: (current)
+
   $ echo a > s/a
 
 should be empty despite change to s/a
@@ -139,14 +158,14 b' add a commit from svn'
   A    externals/other
   Updated external to revision 1.
   
-  Updated to revision 3.
+  Updated to revision 4.
   $ echo xyz >> alpha
   $ svn propset svn:mime-type 'text/xml' alpha
   property 'svn:mime-type' set on 'alpha'
   $ svn ci -m 'amend a from svn'
   Sending        src/alpha
   Transmitting file data .
-  Committed revision 4.
+  Committed revision 5.
   $ cd ../../sub/t
 
 this commit from hg will fail