histedit: add experimental config for using the first word of the commit
This allows users to start a commit with "verb! ..." so that when this is
opened in histedit, the default action will be "verb". For example, "roll! foo"
will default to the action "roll". Currently, we'll allow any known verb to be
used but this is experimental.
#require execbit
$ hg init repo
$ cd repo
$ echo foo > foo
$ chmod 644 foo
$ hg ci -qAm '644'
$ chmod 755 foo
$ hg ci -qAm '755'
reverting to rev 0
$ hg revert -a -r 0
reverting foo
$ hg st
M foo
$ hg diff --git
diff --git a/foo b/foo
old mode 100755
new mode 100644
$ cd ..