# HG changeset patch
# User Laurent Charignon <lcharignon@fb.com>
# Date 1447883069 28800
# Node ID 5eac7ab59b95e5c2dc8dd6a268a51c49540fcbeb
# Parent  53c668dc6b1601c8bda5098df4e33030dbdb454d
rebase: don't rebase obsolete commits with no successor

This patch avoids unnecessary conflicts to resolve during rebase for the users
of changeset evolution.

This patch modifies rebase to skip obsolete commits with no successor.
It introduces a new rebase state 'revpruned' for these revisions that are
being skipped and a new message to inform the user of what is happening.
This feature is gated behind the config flag experimental.rebaseskipobsolete

When an obsolete commit is skipped, the output is:
note: not rebasing 7:360bbaa7d3ce "O", it has no successor

diff -r 53c668dc6b16 -r 5eac7ab59b95 hgext/rebase.py
--- a/hgext/rebase.py	Wed Nov 18 13:46:42 2015 -0800
+++ b/hgext/rebase.py	Wed Nov 18 13:44:29 2015 -0800
@@ -32,6 +32,7 @@
 revignored = -3
 # To do with obsolescence
 revprecursor = -4
+revpruned = -5
 
 cmdtable = {}
 command = cmdutil.command(cmdtable)
@@ -487,6 +488,9 @@
                              targetctx.description().split('\n', 1)[0])
                 msg = _('note: not rebasing %s, already in destination as %s\n')
                 ui.status(msg % (desc, desctarget))
+            elif state[rev] == revpruned:
+                msg = _('note: not rebasing %s, it has no successor\n')
+                ui.status(msg % desc)
             else:
                 ui.status(_('already rebased %s as %s\n') %
                           (desc, repo[state[rev]]))
@@ -676,7 +680,7 @@
     elif p1n in state:
         if state[p1n] == nullmerge:
             p1 = target
-        elif state[p1n] in (revignored, revprecursor):
+        elif state[p1n] in (revignored, revprecursor, revpruned):
             p1 = nearestrebased(repo, p1n, state)
             if p1 is None:
                 p1 = target
@@ -692,7 +696,7 @@
         if p2n in state:
             if p1 == target: # p1n in targetancestors or external
                 p1 = state[p2n]
-            elif state[p2n] in (revignored, revprecursor):
+            elif state[p2n] in (revignored, revprecursor, revpruned):
                 p2 = nearestrebased(repo, p2n, state)
                 if p2 is None:
                     # no ancestors rebased yet, detach
@@ -882,7 +886,7 @@
             else:
                 oldrev, newrev = l.split(':')
                 if newrev in (str(nullmerge), str(revignored),
-                              str(revprecursor)):
+                              str(revprecursor), str(revpruned)):
                     state[repo[oldrev].rev()] = int(newrev)
                 elif newrev == nullid:
                     state[repo[oldrev].rev()] = revtodo
@@ -1066,7 +1070,10 @@
         for ignored in set(rebasedomain) - set(rebaseset):
             state[ignored] = revignored
     for r in obsoletenotrebased:
-        state[r] = revprecursor
+        if obsoletenotrebased[r] is None:
+            state[r] = revpruned
+        else:
+            state[r] = revprecursor
     return repo['.'].rev(), dest.rev(), state
 
 def clearrebased(ui, repo, state, skipped, collapsedas=None):
@@ -1180,7 +1187,9 @@
 
 def _computeobsoletenotrebased(repo, rebasesetrevs, dest):
     """return a mapping obsolete => successor for all obsolete nodes to be
-    rebased that have a successors in the destination"""
+    rebased that have a successors in the destination
+
+    obsolete => None entries in the mapping indicate nodes with no succesor"""
     obsoletenotrebased = {}
 
     # Build a mapping successor => obsolete nodes for the obsolete
@@ -1206,6 +1215,11 @@
         for s in allsuccessors:
             if s in ancs:
                 obsoletenotrebased[allsuccessors[s]] = s
+            elif (s == allsuccessors[s] and
+                  allsuccessors.values().count(s) == 1):
+                # plain prune
+                obsoletenotrebased[s] = None
+
     return obsoletenotrebased
 
 def summaryhook(ui, repo):
diff -r 53c668dc6b16 -r 5eac7ab59b95 tests/test-rebase-obsolete.t
--- a/tests/test-rebase-obsolete.t	Wed Nov 18 13:46:42 2015 -0800
+++ b/tests/test-rebase-obsolete.t	Wed Nov 18 13:44:29 2015 -0800
@@ -659,3 +659,29 @@
   $ hg rebase -d 'desc(B2)'
   note: not rebasing 1:a8b11f55fb19 "B0", already in destination as 2:261e70097290 "B2"
   rebasing 5:1a79b7535141 "D" (tip)
+  $ hg up 4
+  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ echo "O" > O
+  $ hg add O
+  $ hg commit -m O
+  $ echo "P" > P
+  $ hg add P
+  $ hg commit -m P
+  $ hg log -G
+  @  8:8d47583e023f P
+  |
+  o  7:360bbaa7d3ce O
+  |
+  | o  6:9c48361117de D
+  | |
+  o |  4:ff2c4d47b71d C
+  |/
+  o  2:261e70097290 B2
+  |
+  o  0:4a2df7238c3b A
+  
+  $ hg debugobsolete `hg log -r 7 -T '{node}\n'` --config experimental.evolution=all
+  $ hg rebase -d 6 -r "4::"
+  rebasing 4:ff2c4d47b71d "C"
+  note: not rebasing 7:360bbaa7d3ce "O", it has no successor
+  rebasing 8:8d47583e023f "P" (tip)