1 files changed, 73 insertions, 107 deletions

diff --git a/builtin-checkout.c b/builtin-checkout.c
index aec2bc6..411cc51 100644
--- a/builtin-checkout.c
+++ b/builtin-checkout.c
@@ -43,7 +43,7 @@ static int post_checkout_hook(struct commit *old, struct commit *new,
 }
 
 static int update_some(const unsigned char *sha1, const char *base, int baselen,
-		       const char *pathname, unsigned mode, int stage)
+		const char *pathname, unsigned mode, int stage, void *context)
 {
 	int len;
 	struct cache_entry *ce;
@@ -67,7 +67,7 @@ static int update_some(const unsigned char *sha1, const char *base, int baselen,
 
 static int read_tree_some(struct tree *tree, const char **pathspec)
 {
-	read_tree_recursive(tree, "", 0, 0, pathspec, update_some);
+	read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
 
 	/* update the index with the given tree's info
 	 * for all args, expanding wildcards, and exit
@@ -305,97 +305,15 @@ static int merge_working_tree(struct checkout_opts *opts,
 	return 0;
 }
 
-static void report_tracking(struct branch_info *new, struct checkout_opts *opts)
+static void report_tracking(struct branch_info *new)
 {
-	/*
-	 * We have switched to a new branch; is it building on
-	 * top of another branch, and if so does that other branch
-	 * have changes we do not have yet?
-	 */
-	char *base;
-	unsigned char sha1[20];
-	struct commit *ours, *theirs;
-	char symmetric[84];
-	struct rev_info revs;
-	const char *rev_argv[10];
-	int rev_argc;
-	int num_ours, num_theirs;
-	const char *remote_msg;
+	struct strbuf sb = STRBUF_INIT;
 	struct branch *branch = branch_get(new->name);
 
-	/*
-	 * Nothing to report unless we are marked to build on top of
-	 * somebody else.
-	 */
-	if (!branch || !branch->merge || !branch->merge[0] || !branch->merge[0]->dst)
+	if (!format_tracking_info(branch, &sb))
 		return;
-
-	/*
-	 * If what we used to build on no longer exists, there is
-	 * nothing to report.
-	 */
-	base = branch->merge[0]->dst;
-	if (!resolve_ref(base, sha1, 1, NULL))
-		return;
-
-	theirs = lookup_commit(sha1);
-	ours = new->commit;
-	if (!hashcmp(sha1, ours->object.sha1))
-		return; /* we are the same */
-
-	/* Run "rev-list --left-right ours...theirs" internally... */
-	rev_argc = 0;
-	rev_argv[rev_argc++] = NULL;
-	rev_argv[rev_argc++] = "--left-right";
-	rev_argv[rev_argc++] = symmetric;
-	rev_argv[rev_argc++] = "--";
-	rev_argv[rev_argc] = NULL;
-
-	strcpy(symmetric, sha1_to_hex(ours->object.sha1));
-	strcpy(symmetric + 40, "...");
-	strcpy(symmetric + 43, sha1_to_hex(theirs->object.sha1));
-
-	init_revisions(&revs, NULL);
-	setup_revisions(rev_argc, rev_argv, &revs, NULL);
-	prepare_revision_walk(&revs);
-
-	/* ... and count the commits on each side. */
-	num_ours = 0;
-	num_theirs = 0;
-	while (1) {
-		struct commit *c = get_revision(&revs);
-		if (!c)
-			break;
-		if (c->object.flags & SYMMETRIC_LEFT)
-			num_ours++;
-		else
-			num_theirs++;
-	}
-
-	if (!prefixcmp(base, "refs/remotes/")) {
-		remote_msg = " remote";
-		base += strlen("refs/remotes/");
-	} else {
-		remote_msg = "";
-	}
-
-	if (!num_theirs)
-		printf("Your branch is ahead of the tracked%s branch '%s' "
-		       "by %d commit%s.\n",
-		       remote_msg, base,
-		       num_ours, (num_ours == 1) ? "" : "s");
-	else if (!num_ours)
-		printf("Your branch is behind the tracked%s branch '%s' "
-		       "by %d commit%s,\n"
-		       "and can be fast-forwarded.\n",
-		       remote_msg, base,
-		       num_theirs, (num_theirs == 1) ? "" : "s");
-	else
-		printf("Your branch and the tracked%s branch '%s' "
-		       "have diverged,\nand respectively "
-		       "have %d and %d different commit(s) each.\n",
-		       remote_msg, base,
-		       num_ours, num_theirs);
+	fputs(sb.buf, stdout);
+	strbuf_release(&sb);
 }
 
 static void update_refs_for_switch(struct checkout_opts *opts,
@@ -441,7 +359,7 @@ static void update_refs_for_switch(struct checkout_opts *opts,
 	remove_branch_state();
 	strbuf_release(&msg);
 	if (!opts->quiet && (new->path || !strcmp(new->name, "HEAD")))
-		report_tracking(new, opts);
+		report_tracking(new);
 }
 
 static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
@@ -512,6 +430,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		OPT_BOOLEAN('m', NULL, &opts.merge, "merge"),
 		OPT_END(),
 	};
+	int has_dash_dash;
 
 	memset(&opts, 0, sizeof(opts));
 	memset(&new, 0, sizeof(new));
@@ -522,11 +441,55 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
+
+	if (!opts.new_branch && (opts.track != git_branch_track))
+		die("git checkout: --track and --no-track require -b");
+
+	if (opts.force && opts.merge)
+		die("git checkout: -f and -m are incompatible");
+
+	/*
+	 * case 1: git checkout <ref> -- [<paths>]
+	 *
+	 *   <ref> must be a valid tree, everything after the '--' must be
+	 *   a path.
+	 *
+	 * case 2: git checkout -- [<paths>]
+	 *
+	 *   everything after the '--' must be paths.
+	 *
+	 * case 3: git checkout <something> [<paths>]
+	 *
+	 *   With no paths, if <something> is a commit, that is to
+	 *   switch to the branch or detach HEAD at it.
+	 *
+	 *   Otherwise <something> shall not be ambiguous.
+	 *   - If it's *only* a reference, treat it like case (1).
+	 *   - If it's only a path, treat it like case (2).
+	 *   - else: fail.
+	 *
+	 */
 	if (argc) {
+		if (!strcmp(argv[0], "--")) {       /* case (2) */
+			argv++;
+			argc--;
+			goto no_reference;
+		}
+
 		arg = argv[0];
-		if (get_sha1(arg, rev))
-			;
-		else if ((new.commit = lookup_commit_reference_gently(rev, 1))) {
+		has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
+
+		if (get_sha1(arg, rev)) {
+			if (has_dash_dash)          /* case (1) */
+				die("invalid reference: %s", arg);
+			goto no_reference;          /* case (3 -> 2) */
+		}
+
+		/* we can't end up being in (2) anymore, eat the argument */
+		argv++;
+		argc--;
+
+		if ((new.commit = lookup_commit_reference_gently(rev, 1))) {
 			new.name = arg;
 			setup_branch_path(&new);
 			if (resolve_ref(new.path, rev, 1, NULL))
@@ -535,25 +498,28 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 				new.path = NULL;
 			parse_commit(new.commit);
 			source_tree = new.commit->tree;
-			argv++;
-			argc--;
-		} else if ((source_tree = parse_tree_indirect(rev))) {
+		} else
+			source_tree = parse_tree_indirect(rev);
+
+		if (!source_tree)                   /* case (1): want a tree */
+			die("reference is not a tree: %s", arg);
+		if (!has_dash_dash) {/* case (3 -> 1) */
+			/*
+			 * Do not complain the most common case
+			 *	git checkout branch
+			 * even if there happen to be a file called 'branch';
+			 * it would be extremely annoying.
+			 */
+			if (argc)
+				verify_non_filename(NULL, arg);
+		}
+		else {
 			argv++;
 			argc--;
 		}
 	}
 
-	if (argc && !strcmp(argv[0], "--")) {
-		argv++;
-		argc--;
-	}
-
-	if (!opts.new_branch && (opts.track != git_branch_track))
-		die("git checkout: --track and --no-track require -b");
-
-	if (opts.force && opts.merge)
-		die("git checkout: -f and -m are incompatible");
-
+no_reference:
 	if (argc) {
 		const char **pathspec = get_pathspec(prefix, argv);