Patchwork [4,of,4,evolve-ext] fold: rehaul handling of multiple and single revisions (BC)

diff --git a/hgext/evolve.py b/hgext/evolve.py
--- a/hgext/evolve.py
+++ b/hgext/evolve.py
@@ -1716,41 +1716,47 @@ 
         lockmod.release(lock, wlock)
 
 @command('^fold|squash',
-    [('r', 'rev', [], _("explicitly specify the full set of revision to fold")),
+    [('r', 'rev', [], _("revision(s) to fold")),
     ] + commitopts + commitopts2,
     # allow to choose the seed ?
-    _('rev'))
+    _('hg fold [OPTION]... [-r] REV'))
 def fold(ui, repo, *revs, **opts):
-    """Fold multiple revisions into a single one
+    """fold multiple revisions into a single one
 
-    The revisions from your current working directory to the given one are folded
-    into a single successor revision.
+    Folds all revisions between the specified revision and the parent
+    of working directory into a single revision. The folded revisions
+    will be marked as obsolete and replaced by the resulting revision.
 
-    you can alternatively use --rev to explicitly specify revisions to be folded,
-    ignoring the current working directory parent.
+    If multiple revisions are specified, they will all be folded into
+    one, without implicitly folding from the parent of the current
+    working directory.
     """
     revs = list(revs)
-    if revs:
-        if opts.get('rev', ()):
-            raise util.Abort("cannot specify both --rev and a target revision")
-        targets = scmutil.revrange(repo, revs)
-        revs = repo.revs('(%ld::.) or (.::%ld)', targets, targets)
-    elif 'rev' in opts:
-        revs = scmutil.revrange(repo, opts['rev'])
-    else:
-        revs = ()
+    revs.extend(opts['rev'])
     if not revs:
-        ui.write_err('no revision to fold\n')
-        return 1
+        raise util.Abort('no revisions specified')
+
+    revs = scmutil.revrange(repo, revs)
+    if len(revs) == 1:
+        # Try to extend given revision starting from the working directory
+        revs = repo.revs('(%ld::.) or (.::%ld)', revs, revs)
+        if len(revs) == 1:
+            # If that didn't extend, then there's nothing to fold.
+            raise util.Abort('cannot fold current revision with itself\n'
+                             '(specify target revision other than '
+                             'current revision)')
+
     roots = repo.revs('roots(%ld)', revs)
     if len(roots) > 1:
-        raise util.Abort("set has multiple roots")
+        raise util.Abort("cannot fold non-contiguous revisions\n"
+                         "(multiple roots detected)")
     root = repo[roots[0]]
     if root.phase() <= phases.public:
-        raise util.Abort("can't fold public revisions")
+        raise util.Abort("cannot fold public revisions")
     heads = repo.revs('heads(%ld)', revs)
     if len(heads) > 1:
-        raise util.Abort("set has multiple heads")
+        raise util.Abort("cannot fold non-contiguous revisions\n"
+                         "(multiple heads detected)")
     head = repo[heads[0]]
     wlock = lock = None
     try:
diff --git a/tests/test-evolve.t b/tests/test-evolve.t
--- a/tests/test-evolve.t
+++ b/tests/test-evolve.t
@@ -585,10 +585,15 @@ 
 
   $ rm *.orig
   $ hg fold
-  no revision to fold
-  [1]
-  $ hg fold 6 --rev 10
-  abort: cannot specify both --rev and a target revision
+  abort: no revisions specified
+  [255]
+  $ hg fold 5 --rev 10
+  abort: cannot fold non-contiguous revisions
+  (multiple roots detected)
+  [255]
+  $ hg fold -r .
+  abort: cannot fold current revision with itself
+  (specify target revision other than current revision)
   [255]
   $ hg fold 6 # want to run hg fold 6
   2 changesets folded