builtin-am: remove redirection to git-am.sh

At the beginning of the rewrite of git-am.sh to C, in order to not break
existing test scripts that depended on a functional git-am, a
redirection to git-am.sh was introduced that would activate if the
environment variable _GIT_USE_BUILTIN_AM was not defined.

Now that all of git-am.sh's functionality has been re-implemented in
builtin/am.c, remove this redirection, and retire git-am.sh into
contrib/examples/.

Signed-off-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -467,7 +467,6 @@ TEST_PROGRAMS_NEED_X =
 # interactive shell sessions without exporting it.
 unexport CDPATH
 
-SCRIPT_SH += git-am.sh
 SCRIPT_SH += git-bisect.sh
 SCRIPT_SH += git-difftool--helper.sh
 SCRIPT_SH += git-filter-branch.sh

builtin/am.c

@@ -2221,21 +2221,6 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		OPT_END()
 	};
 
-	/*
-	 * NEEDSWORK: Once all the features of git-am.sh have been
-	 * re-implemented in builtin/am.c, this preamble can be removed.
-	 */
-	if (!getenv("_GIT_USE_BUILTIN_AM")) {
-		const char *path = mkpath("%s/git-am", git_exec_path());
-
-		if (sane_execvp(path, (char **)argv) < 0)
-			die_errno("could not exec %s", path);
-	} else {
-		prefix = setup_git_directory();
-		trace_repo_setup(prefix);
-		setup_work_tree();
-	}
-
 	git_config(git_default_config, NULL);
 
 	am_state_init(&state, git_path("rebase-apply"));

git.c

@@ -370,12 +370,7 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 
 static struct cmd_struct commands[] = {
 	{ "add", cmd_add, RUN_SETUP | NEED_WORK_TREE },
-	/*
-	 * NEEDSWORK: Once the redirection to git-am.sh in builtin/am.c has
-	 * been removed, this entry should be changed to
-	 * RUN_SETUP | NEED_WORK_TREE
-	 */
-	{ "am", cmd_am },
+	{ "am", cmd_am, RUN_SETUP | NEED_WORK_TREE },
 	{ "annotate", cmd_annotate, RUN_SETUP },
 	{ "apply", cmd_apply, RUN_SETUP_GENTLY },
 	{ "archive", cmd_archive },