Supplant the "while case ... break ;; esac" idiom

A lot of shell scripts contained stuff starting with

	while case "$#" in 0) break ;; esac

and similar.  I consider breaking out of the condition instead of the
body od the loop ugly, and the implied "true" value of the
non-matching case is not really obvious to humans at first glance.  It
happens not to be obvious to some BSD shells, either, but that's
because they are not POSIX-compliant.  In most cases, this has been
replaced by a straight condition using "test".  "case" has the
advantage of being faster than "test" on vintage shells where "test"
is not a builtin.  Since none of them is likely to run the git
scripts, anyway, the added readability should be worth the change.

A few loops have had their termination condition expressed
differently.

Signed-off-by: David Kastrup <dak@gnu.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/examples/git-gc.sh

@@ -9,7 +9,7 @@ SUBDIRECTORY_OK=Yes
 . git-sh-setup
 
 no_prune=:
-while case $# in 0) break ;; esac
+while test $# != 0
 do
 	case "$1" in
 	--prune)

contrib/examples/git-tag.sh

@@ -14,7 +14,7 @@ username=
 list=
 verify=
 LINES=0
-while case "$#" in 0) break ;; esac
+while test $# != 0
 do
     case "$1" in
     -a)

contrib/examples/git-verify-tag.sh

@@ -5,7 +5,7 @@ SUBDIRECTORY_OK='Yes'
 . git-sh-setup
 
 verbose=
-while case $# in 0) break;; esac
+while test $# != 0
 do
 	case "$1" in
 	-v|--v|--ve|--ver|--verb|--verbo|--verbos|--verbose)