subtree: don't have loose code outside of a function

Shove all of the loose code inside of a main() function.

This comes down to personal preference more than anything else.  A
preference that I've developed over years of maintaining large Bash
scripts, but still a mere personal preference.

In this specific case, it's also moving the `set -- -h`, the `git
rev-parse --parseopt`, and the `. git-sh-setup` to be closer to all
the rest of the argument parsing, which is a readability win on its
own, IMO.

"Ignore space change" is probably helpful when viewing this diff.

Signed-off-by: Luke Shumaker <lukeshu@datawire.io>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/subtree/git-subtree.sh

@@ -4,10 +4,7 @@
 #
 # Copyright (C) 2009 Avery Pennarun <apenwarr@gmail.com>
 #
-if test $# -eq 0
+
-then
-	set -- -h
-fi
 OPTS_SPEC="\
 git subtree add   --prefix=<prefix> <commit>
 git subtree add   --prefix=<prefix> <repository> <ref>
@@ -30,12 +27,8 @@ rejoin        merge the new branch back into HEAD
  options for 'add', 'merge', and 'pull'
 squash        merge subtree changes as a single commit
 "
-eval "$(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)"
 
 PATH=$PATH:$(git --exec-path)
-. git-sh-setup
-
-require_work_tree
 
 quiet=
 branch=
@@ -84,6 +77,15 @@ ensure_single_rev () {
 	fi
 }
 
+main () {
+	if test $# -eq 0
+	then
+		set -- -h
+	fi
+	eval "$(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)"
+	. git-sh-setup
+	require_work_tree
+
 	while test $# -gt 0
 	do
 		opt="$1"
@@ -205,6 +207,9 @@ debug "dir: {$dir}"
 	debug "opts: {$*}"
 	debug
 
+	"cmd_$command" "$@"
+}
+
 cache_setup () {
 	cachedir="$GIT_DIR/subtree-cache/$$"
 	rm -rf "$cachedir" ||
@@ -898,4 +903,4 @@ cmd_push () {
 	fi
 }
 
-"cmd_$command" "$@"
+main "$@"