revert: add support for reverting subrepos

Reverting a subrepo is done by updating it to the revision that is selected on
the parent repo .hgsubstate file.

* ISSUES/TODO:

- reverting added and removed subrepos is not supported yet.
- reverting subrepos is only supported if the --no-backup flag is used (this
limitation will be removed on another patch).
- The behavior of the --all flag has been changed. It now reverts subrepos as
well. Note that this may lead to data loss if the user has a dirty subrepo.

mercurial/cmdutil.py

@@ -1356,8 +1356,6 b' def revert(ui, repo, ctx, parents, *pats'
             if path in names:
                 return
             if path in repo[node].substate:
-                ui.warn("%s: %s\n" % (m.rel(path),
-                    'reverting subrepos is unsupported'))
                 return
             path_ = path + '/'
             for f in names:
@@ -1371,6 +1369,11 b' def revert(ui, repo, ctx, parents, *pats'
             if abs not in names:
                 names[abs] = m.rel(abs), m.exact(abs)
 
+        targetsubs = [s for s in repo[node].substate if m(s)]
+        if targetsubs and not opts.get('no_backup'):
+            msg = _("cannot revert subrepos without --no-backup")
+            raise util.Abort(msg)
+
         m = scmutil.matchfiles(repo, names)
         changes = repo.status(match=m)[:4]
         modified, added, removed, deleted = map(set, changes)
@@ -1499,6 +1502,10 b' def revert(ui, repo, ctx, parents, *pats'
                 checkout(f)
                 normal(f)
 
+            if targetsubs:
+                # Revert the subrepos on the revert list
+                for sub in targetsubs:
+                    ctx.sub(sub).revert(ui, ctx.substate[sub], *pats, **opts)
     finally:
         wlock.release()
 

mercurial/subrepo.py

@@ -368,6 +368,9 b' class abstractsubrepo(object):'
     def forget(self, ui, match, prefix):
         return []
 
+    def revert(self, ui, substate, *pats, **opts):
+        return []
+
 class hgsubrepo(abstractsubrepo):
     def __init__(self, ctx, path, state):
         self._path = path
@@ -573,6 +576,14 b' class hgsubrepo(abstractsubrepo):'
         return cmdutil.forget(ui, self._repo, match,
                               os.path.join(prefix, self._path), True)
 
+    def revert(self, ui, substate, *pats, **opts):
+        # reverting a subrepo is done by updating it to the revision
+        # specified in the corresponding substate dictionary
+        ui.status(_('reverting subrepo %s\n') % substate[0])
+
+        # Update the repo to the revision specified in the given substate
+        self.get(substate, overwrite=True)
+
 class svnsubrepo(abstractsubrepo):
     def __init__(self, ctx, path, state):
         self._path = path

tests/test-subrepo.t

@@ -42,11 +42,14 b" Revert can't (yet) revert subrepos:"
 
   $ echo b > s/a
   $ hg revert s
-  s: reverting subrepos is unsupported
+  abort: cannot revert subrepos without --no-backup
+  [255]
 
 Revert currently ignores subrepos by default
 
   $ hg revert -a
+  abort: cannot revert subrepos without --no-backup
+  [255]
   $ hg revert -R s -a -C
   reverting s/a (glob)