[PATCH 1/3] Prepare execv_git_cmd() for removal of builtins from the filesystem

[Junio C Hamano <gitster@pobox.com>]

Currently, execv_git_cmd() always try running the dashed form, which
means we cannot easily remove the git-foo hardlinks for built-in
commands.  This updates the function to always exec "git foo" form, and
makes sure "git" potty does not infinitely recurse to itself.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 exec_cmd.c |   31 ++++++++++++-------------------
 git.c      |   32 +++++++++++++++++++++++++++++++-
 2 files changed, 43 insertions(+), 20 deletions(-)

diff --git a/exec_cmd.c b/exec_cmd.c
index 2d0a758..10b2908 100644
--- a/exec_cmd.c
+++ b/exec_cmd.c
@@ -65,32 +65,25 @@ void setup_path(const char *cmd_path)
 
 int execv_git_cmd(const char **argv)
 {
-	struct strbuf cmd;
-	const char *tmp;
-
-	strbuf_init(&cmd, 0);
-	strbuf_addf(&cmd, "git-%s", argv[0]);
+	int argc;
+	const char **nargv;
 
-	/*
-	 * argv[0] must be the git command, but the argv array
-	 * belongs to the caller, and may be reused in
-	 * subsequent loop iterations. Save argv[0] and
-	 * restore it on error.
-	 */
-	tmp = argv[0];
-	argv[0] = cmd.buf;
+	for (argc = 0; argv[argc]; argc++)
+		; /* just counting */
+	nargv = xmalloc(sizeof(*nargv) * (argc + 2));
 
-	trace_argv_printf(argv, -1, "trace: exec:");
+	nargv[0] = "git";
+	for (argc = 0; argv[argc]; argc++)
+		nargv[argc + 1] = argv[argc];
+	nargv[argc + 1] = NULL;
+	trace_argv_printf(nargv, -1, "trace: exec:");
 
 	/* execvp() can only ever return if it fails */
-	execvp(cmd.buf, (char **)argv);
+	execvp("git", (char **)nargv);
 
 	trace_printf("trace: exec failed: %s\n", strerror(errno));
 
-	argv[0] = tmp;
-
-	strbuf_release(&cmd);
-
+	free(nargv);
 	return -1;
 }
 
diff --git a/git.c b/git.c
index 01bbbc7..d690426 100644
--- a/git.c
+++ b/git.c
@@ -382,6 +382,36 @@ static void handle_internal_command(int argc, const char **argv)
 	}
 }
 
+static void execv_dashed_external(const char **argv)
+{
+	struct strbuf cmd;
+	const char *tmp;
+
+	strbuf_init(&cmd, 0);
+	strbuf_addf(&cmd, "git-%s", argv[0]);
+
+	/*
+	 * argv[0] must be the git command, but the argv array
+	 * belongs to the caller, and may be reused in
+	 * subsequent loop iterations. Save argv[0] and
+	 * restore it on error.
+	 */
+	tmp = argv[0];
+	argv[0] = cmd.buf;
+
+	trace_argv_printf(argv, -1, "trace: exec:");
+
+	/* execvp() can only ever return if it fails */
+	execvp(cmd.buf, (char **)argv);
+
+	trace_printf("trace: exec failed: %s\n", strerror(errno));
+
+	argv[0] = tmp;
+
+	strbuf_release(&cmd);
+}
+
+
 int main(int argc, const char **argv)
 {
 	const char *cmd = argv[0] ? argv[0] : "git-help";
@@ -445,7 +475,7 @@ int main(int argc, const char **argv)
 		handle_internal_command(argc, argv);
 
 		/* .. then try the external ones */
-		execv_git_cmd(argv);
+		execv_dashed_external(argv);
 
 		/* It could be an alias -- this works around the insanity
 		 * of overriding "git log" with "git show" by having
-- 
1.5.3.6.2090.g4ece0