diff mercurial/commands.py @ 35746:e5b6ba786d83

branch: allow changing branch name to existing name if possible

With the functionality added in previous patch we can change branches of a
revision but not everytime even if it's possible to do so. For example cosider
the following case:

o 3  added a (foo)
o 2  added b (foo)
o 1  added c (bar)
o 0  added d (bar)

Here if I want to change the branch of rev 2,3 to bar, it was not possible and
it will say, "a branch with same name exists".

This patch allows us to change branch of 2,3 to bar. The underlying logic for
changing branch finds the changesets from the revs passed which have no parents
in revs. We only support revsets which have only one such root, so to support
this we check whether the parent of the root has the same name as that of the
new name and if so, we can use the new name to change branches.

Differential Revision: https://phab.mercurial-scm.org/D1913

--- a/mercurial/commands.py	Sun Oct 15 23:08:45 2017 +0530
+++ b/mercurial/commands.py	Fri Jan 19 18:45:20 2018 +0530
@@ -1055,11 +1055,6 @@
 
             scmutil.checknewlabel(repo, label, 'branch')
             if revs:
-                # XXX: we should allow setting name to existing branch if the
-                # branch of root of the revs is same as the new branch name
-                if label in repo.branchmap():
-                    raise error.Abort(_('a branch of the same'
-                                        ' name already exists'))
                 return cmdutil.changebranch(ui, repo, revs, label)
 
             if not opts.get('force') and label in repo.branchmap():