checkout: reorder option handling

checkout operates in three different modes. On top of that it tries to
be smart by guessing the branch name for switching. This results in
messy option handling code. This patch reorders it so that

 - cmd_checkout() is responsible for parsing, preparing input and
   determining mode

 - Code of each mode is in checkout_paths() and checkout_branch(),
   where sanity checks are performed

Another slight improvement is always print branch name (or commit
name) when printing errors related ot them. This helps catch the case
where an option is mistaken as branch/commit.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 112 insertions, 77 deletions

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 78abaeb92d..b4030121c8 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -217,7 +217,8 @@ static int checkout_merged(int pos, struct checkout *state)
 	return status;
 }
 
-static int checkout_paths(const struct checkout_opts *opts)
+static int checkout_paths(const struct checkout_opts *opts,
+			  const char *revision)
 {
 	int pos;
 	struct checkout state;
@@ -229,7 +230,35 @@ static int checkout_paths(const struct checkout_opts *opts)
 	int stage = opts->writeout_stage;
 	int merge = opts->merge;
 	int newfd;
-	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
+	struct lock_file *lock_file;
+
+	if (opts->track != BRANCH_TRACK_UNSPECIFIED)
+		die(_("'%s' cannot be used with updating paths"), "--track");
+
+	if (opts->new_branch_log)
+		die(_("'%s' cannot be used with updating paths"), "-l");
+
+	if (opts->force && opts->patch_mode)
+		die(_("'%s' cannot be used with updating paths"), "-f");
+
+	if (opts->force_detach)
+		die(_("'%s' cannot be used with updating paths"), "--detach");
+
+	if (opts->merge && opts->patch_mode)
+		die(_("'%s' cannot be used with %s"), "--merge", "--patch");
+
+	if (opts->force && opts->merge)
+		die(_("'%s' cannot be used with %s"), "-f", "-m");
+
+	if (opts->new_branch)
+		die(_("Cannot update paths and switch to branch '%s' at the same time."),
+		    opts->new_branch);
+
+	if (opts->patch_mode)
+		return run_add_interactive(revision, "--patch=checkout",
+					   opts->pathspec);
+
+	lock_file = xcalloc(1, sizeof(struct lock_file));
 
 	newfd = hold_locked_index(lock_file, 1);
 	if (read_cache_preload(opts->pathspec) < 0)
@@ -763,11 +792,6 @@ static int git_checkout_config(const char *var, const char *value, void *cb)
 	return git_xmerge_config(var, value, NULL);
 }
 
-static int interactive_checkout(const char *revision, const char **pathspec)
-{
-	return run_add_interactive(revision, "--patch=checkout", pathspec);
-}
-
 struct tracking_name_data {
 	const char *name;
 	char *remote;
@@ -930,6 +954,51 @@ static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
 	return status;
 }
 
+static int checkout_branch(struct checkout_opts *opts,
+			   struct branch_info *new)
+{
+	if (opts->pathspec)
+		die(_("paths cannot be used with switching branches"));
+
+	if (opts->patch_mode)
+		die(_("'%s' cannot be used with switching branches"),
+		    "--patch");
+
+	if (opts->writeout_stage)
+		die(_("'%s' cannot be used with switching branches"),
+		    "--ours/--theirs");
+
+	if (opts->force && opts->merge)
+		die(_("'%s' cannot be used with '%s'"), "-f", "-m");
+
+	if (opts->force_detach && opts->new_branch)
+		die(_("'%s' cannot be used with '%s'"),
+		    "--detach", "-b/-B/--orphan");
+
+	if (opts->new_orphan_branch) {
+		if (opts->track != BRANCH_TRACK_UNSPECIFIED)
+			die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
+	} else if (opts->force_detach) {
+		if (opts->track != BRANCH_TRACK_UNSPECIFIED)
+			die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
+	} else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
+		opts->track = git_branch_track;
+
+	if (new->name && !new->commit)
+		die(_("Cannot switch branch to a non-commit '%s'"),
+		    new->name);
+
+	if (!new->commit && opts->new_branch) {
+		unsigned char rev[20];
+		int flag;
+
+		if (!read_ref_full("HEAD", rev, 0, &flag) &&
+		    (flag & REF_ISSYMREF) && is_null_sha1(rev))
+			return switch_unborn_to_new_branch(opts);
+	}
+	return switch_branches(opts, new);
+}
+
 int cmd_checkout(int argc, const char **argv, const char *prefix)
 {
 	struct checkout_opts opts;
@@ -976,26 +1045,27 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
-	/* we can assume from now on new_branch = !new_branch_force */
-	if (opts.new_branch && opts.new_branch_force)
-		die(_("-B cannot be used with -b"));
+	if (conflict_style) {
+		opts.merge = 1; /* implied */
+		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
+	}
 
-	/* copy -B over to -b, so that we can just check the latter */
+	if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
+		die(_("-b, -B and --orphan are mutually exclusive"));
+
+	/*
+	 * From here on, new_branch will contain the branch to be checked out,
+	 * and new_branch_force and new_orphan_branch will tell us which one of
+	 * -b/-B/--orphan is being used.
+	 */
 	if (opts.new_branch_force)
 		opts.new_branch = opts.new_branch_force;
 
-	if (opts.patch_mode && (opts.track > 0 || opts.new_branch
-			   || opts.new_branch_log || opts.merge || opts.force
-			   || opts.force_detach))
-		die (_("--patch is incompatible with all other options"));
-
-	if (opts.force_detach && (opts.new_branch || opts.new_orphan_branch))
-		die(_("--detach cannot be used with -b/-B/--orphan"));
-	if (opts.force_detach && 0 < opts.track)
-		die(_("--detach cannot be used with -t"));
+	if (opts.new_orphan_branch)
+		opts.new_branch = opts.new_orphan_branch;
 
-	/* --track without -b should DWIM */
-	if (0 < opts.track && !opts.new_branch) {
+	/* --track without -b/-B/--orphan should DWIM */
+	if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
 		const char *argv0 = argv[0];
 		if (!argc || !strcmp(argv0, "--"))
 			die (_("--track needs a branch name"));
@@ -1009,22 +1079,6 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		opts.new_branch = argv0 + 1;
 	}
 
-	if (opts.new_orphan_branch) {
-		if (opts.new_branch)
-			die(_("--orphan and -b|-B are mutually exclusive"));
-		if (opts.track > 0)
-			die(_("--orphan cannot be used with -t"));
-		opts.new_branch = opts.new_orphan_branch;
-	}
-
-	if (conflict_style) {
-		opts.merge = 1; /* implied */
-		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
-	}
-
-	if (opts.force && opts.merge)
-		die(_("git checkout: -f and -m are incompatible"));
-
 	/*
 	 * Extract branch name from command line arguments, so
 	 * all that is left is pathspecs.
@@ -1052,62 +1106,43 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		argc -= n;
 	}
 
-	if (opts.track == BRANCH_TRACK_UNSPECIFIED)
-		opts.track = git_branch_track;
-
 	if (argc) {
 		opts.pathspec = get_pathspec(prefix, argv);
 
 		if (!opts.pathspec)
 			die(_("invalid path specification"));
 
-		if (opts.patch_mode)
-			return interactive_checkout(new.name, opts.pathspec);
-
-		/* Checkout paths */
-		if (opts.new_branch) {
-			if (argc == 1) {
-				die(_("git checkout: updating paths is incompatible with switching branches.\nDid you intend to checkout '%s' which can not be resolved as commit?"), argv[0]);
-			} else {
-				die(_("git checkout: updating paths is incompatible with switching branches."));
-			}
-		}
+		/*
+		 * Try to give more helpful suggestion.
+		 * new_branch && argc > 1 will be caught later.
+		 */
+		if (opts.new_branch && argc == 1)
+			die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
+			      "Did you intend to checkout '%s' which can not be resolved as commit?"),
+			    opts.new_branch, argv[0]);
 
 		if (opts.force_detach)
-			die(_("git checkout: --detach does not take a path argument"));
+			die(_("git checkout: --detach does not take a path argument '%s'"),
+			    argv[0]);
 
 		if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
-			die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\nchecking out of the index."));
-
-		return checkout_paths(&opts);
+			die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
+			      "checking out of the index."));
 	}
 
-	if (opts.patch_mode)
-		return interactive_checkout(new.name, NULL);
-
 	if (opts.new_branch) {
 		struct strbuf buf = STRBUF_INIT;
 
-		opts.branch_exists = validate_new_branchname(opts.new_branch, &buf,
-							     !!opts.new_branch_force,
-							     !!opts.new_branch_force);
+		opts.branch_exists =
+			validate_new_branchname(opts.new_branch, &buf,
+						!!opts.new_branch_force,
+						!!opts.new_branch_force);
 
 		strbuf_release(&buf);
 	}
 
-	if (new.name && !new.commit) {
-		die(_("Cannot switch branch to a non-commit."));
-	}
-	if (opts.writeout_stage)
-		die(_("--ours/--theirs is incompatible with switching branches."));
-
-	if (!new.commit && opts.new_branch) {
-		unsigned char rev[20];
-		int flag;
-
-		if (!read_ref_full("HEAD", rev, 0, &flag) &&
-		    (flag & REF_ISSYMREF) && is_null_sha1(rev))
-			return switch_unborn_to_new_branch(&opts);
-	}
-	return switch_branches(&opts, &new);
+	if (opts.patch_mode || opts.pathspec)
+		return checkout_paths(&opts, new.name);
+	else
+		return checkout_branch(&opts, &new);
 }