graphlog: fix --follow --rev combinations
The previous behaviour of --follow was really a subset of what is really
happening in log command:
- If --rev is not passed, default to '.:0'
- Resolve --rev into a revision list "revs"
- Set the starting revision to revs[0]
- If revs[1] > revs[0] keep descendants(revs[0]) in revs, otherwise keep
ancestors.
http://mercurial.selenic.com/bts/issue619
$ hg init
$ echo a > a
$ hg ci -Ama
adding a
$ echo b > b
$ hg branch b
marked working directory as branch b
(branches are permanent and global, did you want a bookmark?)
$ hg ci -Amb
adding b
$ hg co -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Fast-forward:
$ hg merge b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -Ammerge
Bogus fast-forward should fail:
$ hg merge b
abort: merging with a working directory ancestor has no effect
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