revert: properly revert to ancestor of p2 during merge (issue5052)

During merge, added (from one perspective) file can be reported as "modified".
To work around that, revert was testing if modified file were present in the
parent manifest and marking them as "added" in this case. However, we should be
checking against the target revision manifest instead. Otherwise see file as
"newly added" even if they exist in the target revision.

That revert behavior regressed in 06fbd9518bc5.

mercurial/cmdutil.py

@@ -2846,10 +2846,6 b' def revert(ui, repo, ctx, parents, *pats'
     mf = ctx.manifest()
     if node == p2:
         parent = p2
-    if node == parent:
-        pmf = mf
-    else:
-        pmf = None
 
     # need all matching names in dirstate and manifest of target rev,
     # so have to walk both. do not print errors if files exist in one
@@ -2964,11 +2960,7 b' def revert(ui, repo, ctx, parents, *pats'
         # in case of merge, files that are actually added can be reported as
         # modified, we need to post process the result
         if p2 != nullid:
-            if pmf is None:
-                # only need parent manifest in the merge case,
-                # so do not read by default
-                pmf = repo[parent].manifest()
-            mergeadd = dsmodified - set(pmf)
+            mergeadd = dsmodified - smf
             dsadded |= mergeadd
             dsmodified -= mergeadd
 

tests/test-revert.t

@@ -1076,3 +1076,72 b' check resulting directory against the --'
   $ cd ..
   $ diff -U 0 -- content-base-all.txt content-base-explicit.txt | grep _
   [1]
+
+Revert to an ancestor of P2 during a merge (issue5052)
+-----------------------------------------------------
+
+(prepare the repository)
+
+  $ hg init issue5052
+  $ cd issue5052
+  $ echo '.\.orig' > .hgignore
+  $ echo 0 > root
+  $ hg ci -qAm C0
+  $ echo 0 > A
+  $ hg ci -qAm C1
+  $ echo 1 >> A
+  $ hg ci -qm C2
+  $ hg up -q 0
+  $ echo 1 > B
+  $ hg ci -qAm C3
+  $ hg status --rev 'ancestor(.,2)' --rev 2
+  A A
+  $ hg log -G -T '{rev} ({files})\n'
+  @  3 (B)
+  |
+  | o  2 (A)
+  | |
+  | o  1 (A)
+  |/
+  o  0 (.hgignore root)
+  
+
+actual tests: reverting to something else than a merge parent
+
+  $ hg merge
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+
+  $ hg status --rev 'p1()'
+  M A
+  $ hg status --rev 'p2()'
+  A B
+  $ hg status --rev '1'
+  M A
+  A B
+  $ hg revert --rev 1 --all
+  reverting A
+  removing B
+  $ hg status --rev 1
+
+From the other parents
+
+  $ hg up -C 'p2()'
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+
+  $ hg status --rev 'p1()'
+  M B
+  $ hg status --rev 'p2()'
+  A A
+  $ hg status --rev '1'
+  M A
+  A B
+  $ hg revert --rev 1 --all
+  reverting A
+  removing B
+  $ hg status --rev 1
+
+  $ cd ..