subrepo/svn: abort on commit with missing file (issue3029)

Previous code was printing a traceback because it expected some error output
from svn. But sometimes our definition of "changed" differs with the subversion
one. For instance, subversion ignores missing files when committing. And when
there are only missing files, svn commit will be a successful no-op with no
output. Still, we should stick to our definition including missing files in
changes as doing otherwise could cause surprising behaviour for the user.

mercurial/subrepo.py

@@ -726,6 +726,12 b' class svnsubrepo(abstractsubrepo):'
         self._ui.status(commitinfo)
         newrev = re.search('Committed revision ([0-9]+).', commitinfo)
         if not newrev:
+            if not commitinfo.strip():
+                # Sometimes, our definition of "changed" differs from
+                # svn one. For instance, svn ignores missing files
+                # when committing. If there are only missing files, no
+                # commit is made, no output and no error code.
+                raise util.Abort(_('failed to commit svn changes'))
             raise util.Abort(commitinfo.splitlines()[-1])
         newrev = newrev.groups()[0]
         self._ui.status(self._svncommand(['update', '-r', newrev])[0])

tests/test-subrepo-svn.t

@@ -120,6 +120,15 b' change file in svn and hg, commit'
    source   file://*/svn-repo/src (glob)
    revision 2
 
+missing svn file, commit should fail
+
+  $ rm s/alpha
+  $ hg commit --subrepos -m 'abort on missing file'
+  committing subrepository s
+  abort: failed to commit svn changes
+  [255]
+  $ svn revert s/alpha > /dev/null
+
 add an unrelated revision in svn and update the subrepo to without
 bringing any changes.