[PATCH] Add an --argscmd flag to get the list of refs to show

[PATCH] Add an --argscmd flag to get the list of refs to show

This allows gitk to be used to display a different set of refs each
the display is refreshed.  This is useful when gitk is called from
other porcelain suites, for doing such things as displaying the set of
patches in a patch stack.

The user specifies a command as the argument to the --argscmd option.
The command is run initially and each time the display is refreshed,
and is expected to generate a list of commit IDs, one per line.  Those
commits are appended to the commits passed on the command-line when
constructing the git log command to be executed.

The command is considered to be an attribute of a view, and has its
own field in the saved view, and an edit field in the view editor.

Signed-off-by: Yann Dirson <ydirson@altern.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>