tests/test-symlink-basic.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.

abort: dangling: file not tracked!
changeset:   0:cabd88b706fc
tag:         tip
user:        test
date:        Thu Jan 01 00:00:00 1970 +0000
files:       dangling
description:
add symlink


2564acbe54bbbedfbf608479340b359f04597f80 644 @ dangling
% rev 0:
dangling -> nothing
% rev 1:
dangling -> void
% modifying link
dangling -> empty
% reverting to rev 0:
reverting dangling
dangling -> nothing
% backups:
dangling.orig -> empty
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% copies
copying dangling to dangling2
A dangling2
  dangling
dangling -> void
dangling2 -> void
% issue995
0 files updated, 0 files merged, 0 files removed, 0 files unresolved