gitk: Add visiblerefs option, which lists always-shown branches
gitk: Add visiblerefs option, which lists always-shown branches

When many branches contain a commit, the branches used to be shown in
the form "A, B and many more", where A, B can be master of current
HEAD. But there are more which might be interesting to always know about.
For example, "origin/master".

The new option, visiblerefs, is stored in ~/.gitk. It contains a list
of references which are always shown before "and many more" if they
contain the commit. By default it is `{"master"}', which is compatible
with previous behavior.

Signed-off-by: Max Kirillov <0706025b2bbcec1ed8d64822f4eccd96314938d0@max630.net>
Signed-off-by: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git