new gitk feature

[Paul Mackerras <paulus@samba.org>]

I just pushed some changes to gitk which add a new feature, the
ability to have multiple "views" of a repository.  Each view is a
subgraph of the full graph.  At the moment the only subgraph that you
can specify is the subgraph containing the commits that affect a
specified set of files or directories.  You can switch between views
quickly, and if the currently selected commit exists in the new view
when you switch views, it is selected in the new view.  There is one
view which always exists, the "All files" view.  If files or
directories are specified on the command line, a "Command line" view
is automatically created and selected at startup.

Thus, for the kernel repository I can have a "PPC" view which shows
changes to arch/powerpc, include/asm-powerpc etc.  When looking at a
commit in that view, I can switch to the "All files" view to see where
that commit fits in the overall history.

There is a "View" menu which contains the menu items for creating,
deleting, editing and selecting views.  If you check the "Remember
this view" box, gitk will write the definition of the view to your
~/.gitk file, and it will be automatically put in the list on startup.

I plan to add various other kinds of views, for example, a view that
shows only the commits that affect a selected file (or part of a file,
perhaps), and a view that shows just the current commit together with
all the commits that have tags.  (The latter will require some help
from git-rev-list. :)

Paul.