[PATCH] convert: filemap must preserve fast-forward merges (issue3340)

[Patrick Mezard]

# HG changeset patch
# User Patrick Mezard <patrick at mezard.eu>
# Date 1338141206 -7200
# Branch stable
# Node ID db0660915e353f8a87ed11fb87660a794c0bab45
# Parent  30e46d7138de0acb2d811162c1cf3441afe1687e
convert: filemap must preserve fast-forward merges (issue3340)

When running convert with a filemap, revisions which changes were
filtered out and not closing branch were discarded. Unfortunately, this
also discards fast-forward merges between named branches, which are
fairly important, especially for head revisions.

This patch makes --filemap preserve fast-forward merges between distinct
named branches, even if the merge brings nothing but a branch switch,
and even if the empty merge comes from ancestors being filtered by the
filemap.

diff --git a/hgext/convert/filemap.py b/hgext/convert/filemap.py
--- a/hgext/convert/filemap.py
+++ b/hgext/convert/filemap.py
@@ -297,6 +297,7 @@
         # - is not an ancestor of the mapped versions of the other parents
         mparents = []
         wp = None
+        branch = self.commits[rev].branch
         for i, p1 in enumerate(parents):
             mp1 = self.parentmap[p1]
             if mp1 == SKIPREV or mp1 in mparents:
@@ -305,7 +306,9 @@
                 if p1 == p2 or mp1 == self.parentmap[p2]:
                     continue
                 if mp1 in self.wantedancestors[p2]:
-                    break
+                    # Discard fast-forward in the same branch
+                    if self.commits[p2].branch == branch:
+                        break
             else:
                 mparents.append(mp1)
                 wp = i
@@ -319,7 +322,6 @@
         if 'close' in self.commits[rev].extra:
             # A branch closing revision is only useful if one of its
             # parents belong to the branch being closed
-            branch = self.commits[rev].branch
             pbranches = [self._cachedcommit(p).branch for p in mparents]
             if branch in pbranches:
                 closed = True
diff --git a/tests/test-convert-filemap.t b/tests/test-convert-filemap.t
--- a/tests/test-convert-filemap.t
+++ b/tests/test-convert-filemap.t
@@ -375,3 +375,88 @@
   |
   o  0 "addb" files: b
   
+test fast-forward
+
+  $ hg init fastforward
+  $ cd fastforward
+  $ echo a > a
+  $ echo b > b
+  $ hg ci -Am adda
+  adding a
+  adding b
+  $ hg branch foo
+  marked working directory as branch foo
+  (branches are permanent and global, did you want a bookmark?)
+  $ echo a >> a
+  $ hg ci -m branchfoo
+  $ hg up -qC 0
+  $ echo b >> b
+  $ hg ci -m changeb
+  $ hg merge foo
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg ci -m mergefoo
+  $ hg branch bar
+  marked working directory as branch bar
+  (branches are permanent and global, did you want a bookmark?)
+  $ echo a >> a
+  $ hg ci -m branchbar
+  $ hg up -qC 3
+  $ hg merge bar
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg ci -m fastforwardbar
+  $ hg up -qC 1
+  $ echo b >> b
+  $ hg ci -m changebagain
+  $ hg up -qC 5
+  $ hg merge --tool internal:local 6
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg ci -m merge6
+  $ cd ..
+  $ glog -R fastforward
+  @    7 "merge6" files:
+  |\
+  | o  6 "changebagain" files: b
+  | |
+  o |    5 "fastforwardbar" files:
+  |\ \
+  | o |  4 "branchbar" files: a
+  |/ /
+  o |  3 "mergefoo" files:
+  |\|
+  o |  2 "changeb" files: b
+  | |
+  | o  1 "branchfoo" files: a
+  |/
+  o  0 "adda" files: a b
+  
+
+  $ cat > filemap <<EOF
+  > include a
+  > EOF
+  $ hg convert --filemap filemap fastforward fastforward1
+  initializing destination fastforward1 repository
+  scanning source...
+  sorting...
+  converting...
+  7 adda
+  6 branchfoo
+  5 changeb
+  4 mergefoo
+  3 branchbar
+  2 fastforwardbar
+  1 changebagain
+  0 merge6
+  $ glog -R fastforward1
+  o    4 "fastforwardbar" files:
+  |\
+  | o  3 "branchbar" files: a
+  |/
+  o    2 "mergefoo" files:
+  |\
+  | o  1 "branchfoo" files: a
+  |/
+  o  0 "adda" files: a
+