[PATCH 3 of 5 RFC] revset: add a predicate for finding grafts

[Matt Harbison]

# HG changeset patch
# User Matt Harbison <matt_harbison at yahoo.com>
# Date 1336879967 14400
# Node ID 2612b6d41579adce0df8f6b744f2879868125b5b
# Parent  eabdd37ccf00e44c0f94c2494fa82f5dce773e2a
revset: add a predicate for finding grafts

This selects changesets added because of grafts.  If a revision is specified,
the set will be empty if that revision is not the source of a graft, or it will
contain a destination changeset for each time the specified revision was
grafted.  This can be useful for figuring out where a particular changeset has
been propagated.

The source revision may be a local identifier, the short changeset hash or the
full hash.  The revision must exist, or the query is aborted.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -561,6 +561,23 @@
     getargs(x, 0, 0, _("all takes no arguments"))
     return subset
 
+def graftof(repo, subset, x):
+    """``graftof([rev])``
+    Changesets grafted from rev, or all grafted changesets.
+    """
+
+    # i18n: "graftof" is a keyword
+    l = getargs(x, 0, 1, _('graftof takes one or no arguments'))
+
+    # i18n: "graftof" is a keyword
+    rev = l and getrev(repo, l[0], _('graftof requires a revision')) or None
+
+    def _matchvalue(r):
+        source = repo[r].extra().get('source', None)
+        return source is not None and (rev is None or rev == source)
+
+    return [r for r in subset if _matchvalue(r)]
+
 def grep(repo, subset, x):
     """``grep(regex)``
     Like ``keyword(string)`` but accepts a regex. Use ``grep(r'...')``
@@ -1199,6 +1216,7 @@
     "first": first,
     "follow": follow,
     "_followfirst": _followfirst,
+    "graftof":graftof,
     "grep": grep,
     "head": head,
     "heads": heads,