tests/test-merge-local.out

prepush: add more precise error messages

Part of the patch is from [e-mail]

- indicate the branch name where there are multiple heads
- give better advice when hitting a possible race, where new heads are added
  between discovery and the call to branchmap(). In that case, asking the user
  to merge isn't helpful, since only remote has the changes.

# revision 0
adding copy
adding move
adding remove
adding unchanged
adding zzz1_merge_ok
adding zzz2_merge_bad
# revision 1
# local changes to revision 0
4 files updated, 0 files merged, 3 files removed, 0 files unresolved
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new last line
--- a/zzz2_merge_bad
+++ b/zzz2_merge_bad
+another last line
M zzz1_merge_ok
M zzz2_merge_bad
# local merge with bad merge tool
merging zzz1_merge_ok
merging zzz2_merge_bad
merging zzz2_merge_bad failed!
3 files updated, 1 files merged, 2 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
merging zzz1_merge_ok
merging zzz2_merge_bad
2 files updated, 2 files merged, 3 files removed, 0 files unresolved
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new first line
+new last line
--- a/zzz2_merge_bad
+++ b/zzz2_merge_bad
+another last line
M zzz1_merge_ok
M zzz2_merge_bad
# local merge with conflicts
merging zzz1_merge_ok
merging zzz2_merge_bad
warning: conflicts during merge.
merging zzz2_merge_bad failed!
3 files updated, 1 files merged, 2 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
merging zzz1_merge_ok
merging zzz2_merge_bad
2 files updated, 2 files merged, 3 files removed, 0 files unresolved
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new first line
+new last line
--- a/zzz2_merge_bad
+++ b/zzz2_merge_bad
+another last line
+=======
+new last line
M zzz1_merge_ok
M zzz2_merge_bad
# local merge without conflicts
merging zzz1_merge_ok
4 files updated, 1 files merged, 2 files removed, 0 files unresolved
--- a/zzz1_merge_ok
+++ b/zzz1_merge_ok
+new last line
M zzz1_merge_ok
? zzz2_merge_bad.orig