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-rw-r--r--builtin/checkout.c853
1 files changed, 853 insertions, 0 deletions
diff --git a/builtin/checkout.c b/builtin/checkout.c
new file mode 100644
index 0000000..c5ab783
--- /dev/null
+++ b/builtin/checkout.c
@@ -0,0 +1,853 @@
+#include "cache.h"
+#include "builtin.h"
+#include "parse-options.h"
+#include "refs.h"
+#include "commit.h"
+#include "tree.h"
+#include "tree-walk.h"
+#include "cache-tree.h"
+#include "unpack-trees.h"
+#include "dir.h"
+#include "run-command.h"
+#include "merge-recursive.h"
+#include "branch.h"
+#include "diff.h"
+#include "revision.h"
+#include "remote.h"
+#include "blob.h"
+#include "xdiff-interface.h"
+#include "ll-merge.h"
+#include "resolve-undo.h"
+
+static const char * const checkout_usage[] = {
+ "git checkout [options] <branch>",
+ "git checkout [options] [<branch>] -- <file>...",
+ NULL,
+};
+
+struct checkout_opts {
+ int quiet;
+ int merge;
+ int force;
+ int writeout_stage;
+ int writeout_error;
+
+ const char *new_branch;
+ int new_branch_log;
+ enum branch_track track;
+};
+
+static int post_checkout_hook(struct commit *old, struct commit *new,
+ int changed)
+{
+ return run_hook(NULL, "post-checkout",
+ sha1_to_hex(old ? old->object.sha1 : null_sha1),
+ sha1_to_hex(new ? new->object.sha1 : null_sha1),
+ changed ? "1" : "0", NULL);
+ /* "new" can be NULL when checking out from the index before
+ a commit exists. */
+
+}
+
+static int update_some(const unsigned char *sha1, const char *base, int baselen,
+ const char *pathname, unsigned mode, int stage, void *context)
+{
+ int len;
+ struct cache_entry *ce;
+
+ if (S_ISDIR(mode))
+ return READ_TREE_RECURSIVE;
+
+ len = baselen + strlen(pathname);
+ ce = xcalloc(1, cache_entry_size(len));
+ hashcpy(ce->sha1, sha1);
+ memcpy(ce->name, base, baselen);
+ memcpy(ce->name + baselen, pathname, len - baselen);
+ ce->ce_flags = create_ce_flags(len, 0);
+ ce->ce_mode = create_ce_mode(mode);
+ add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
+ return 0;
+}
+
+static int read_tree_some(struct tree *tree, const char **pathspec)
+{
+ 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
+ * with any non-zero return code.
+ */
+ return 0;
+}
+
+static int skip_same_name(struct cache_entry *ce, int pos)
+{
+ while (++pos < active_nr &&
+ !strcmp(active_cache[pos]->name, ce->name))
+ ; /* skip */
+ return pos;
+}
+
+static int check_stage(int stage, struct cache_entry *ce, int pos)
+{
+ while (pos < active_nr &&
+ !strcmp(active_cache[pos]->name, ce->name)) {
+ if (ce_stage(active_cache[pos]) == stage)
+ return 0;
+ pos++;
+ }
+ return error("path '%s' does not have %s version",
+ ce->name,
+ (stage == 2) ? "our" : "their");
+}
+
+static int check_all_stages(struct cache_entry *ce, int pos)
+{
+ if (ce_stage(ce) != 1 ||
+ active_nr <= pos + 2 ||
+ strcmp(active_cache[pos+1]->name, ce->name) ||
+ ce_stage(active_cache[pos+1]) != 2 ||
+ strcmp(active_cache[pos+2]->name, ce->name) ||
+ ce_stage(active_cache[pos+2]) != 3)
+ return error("path '%s' does not have all three versions",
+ ce->name);
+ return 0;
+}
+
+static int checkout_stage(int stage, struct cache_entry *ce, int pos,
+ struct checkout *state)
+{
+ while (pos < active_nr &&
+ !strcmp(active_cache[pos]->name, ce->name)) {
+ if (ce_stage(active_cache[pos]) == stage)
+ return checkout_entry(active_cache[pos], state, NULL);
+ pos++;
+ }
+ return error("path '%s' does not have %s version",
+ ce->name,
+ (stage == 2) ? "our" : "their");
+}
+
+/* NEEDSWORK: share with merge-recursive */
+static void fill_mm(const unsigned char *sha1, mmfile_t *mm)
+{
+ unsigned long size;
+ enum object_type type;
+
+ if (!hashcmp(sha1, null_sha1)) {
+ mm->ptr = xstrdup("");
+ mm->size = 0;
+ return;
+ }
+
+ mm->ptr = read_sha1_file(sha1, &type, &size);
+ if (!mm->ptr || type != OBJ_BLOB)
+ die("unable to read blob object %s", sha1_to_hex(sha1));
+ mm->size = size;
+}
+
+static int checkout_merged(int pos, struct checkout *state)
+{
+ struct cache_entry *ce = active_cache[pos];
+ const char *path = ce->name;
+ mmfile_t ancestor, ours, theirs;
+ int status;
+ unsigned char sha1[20];
+ mmbuffer_t result_buf;
+
+ if (ce_stage(ce) != 1 ||
+ active_nr <= pos + 2 ||
+ strcmp(active_cache[pos+1]->name, path) ||
+ ce_stage(active_cache[pos+1]) != 2 ||
+ strcmp(active_cache[pos+2]->name, path) ||
+ ce_stage(active_cache[pos+2]) != 3)
+ return error("path '%s' does not have all 3 versions", path);
+
+ fill_mm(active_cache[pos]->sha1, &ancestor);
+ fill_mm(active_cache[pos+1]->sha1, &ours);
+ fill_mm(active_cache[pos+2]->sha1, &theirs);
+
+ status = ll_merge(&result_buf, path, &ancestor,
+ &ours, "ours", &theirs, "theirs", 0);
+ free(ancestor.ptr);
+ free(ours.ptr);
+ free(theirs.ptr);
+ if (status < 0 || !result_buf.ptr) {
+ free(result_buf.ptr);
+ return error("path '%s': cannot merge", path);
+ }
+
+ /*
+ * NEEDSWORK:
+ * There is absolutely no reason to write this as a blob object
+ * and create a phony cache entry just to leak. This hack is
+ * primarily to get to the write_entry() machinery that massages
+ * the contents to work-tree format and writes out which only
+ * allows it for a cache entry. The code in write_entry() needs
+ * to be refactored to allow us to feed a <buffer, size, mode>
+ * instead of a cache entry. Such a refactoring would help
+ * merge_recursive as well (it also writes the merge result to the
+ * object database even when it may contain conflicts).
+ */
+ if (write_sha1_file(result_buf.ptr, result_buf.size,
+ blob_type, sha1))
+ die("Unable to add merge result for '%s'", path);
+ ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
+ sha1,
+ path, 2, 0);
+ if (!ce)
+ die("make_cache_entry failed for path '%s'", path);
+ status = checkout_entry(ce, state, NULL);
+ return status;
+}
+
+static int checkout_paths(struct tree *source_tree, const char **pathspec,
+ struct checkout_opts *opts)
+{
+ int pos;
+ struct checkout state;
+ static char *ps_matched;
+ unsigned char rev[20];
+ int flag;
+ struct commit *head;
+ int errs = 0;
+ int stage = opts->writeout_stage;
+ int merge = opts->merge;
+ int newfd;
+ struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
+
+ newfd = hold_locked_index(lock_file, 1);
+ if (read_cache_preload(pathspec) < 0)
+ return error("corrupt index file");
+
+ if (source_tree)
+ read_tree_some(source_tree, pathspec);
+
+ for (pos = 0; pathspec[pos]; pos++)
+ ;
+ ps_matched = xcalloc(1, pos);
+
+ for (pos = 0; pos < active_nr; pos++) {
+ struct cache_entry *ce = active_cache[pos];
+ match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
+ }
+
+ if (report_path_error(ps_matched, pathspec, 0))
+ return 1;
+
+ /* "checkout -m path" to recreate conflicted state */
+ if (opts->merge)
+ unmerge_cache(pathspec);
+
+ /* Any unmerged paths? */
+ for (pos = 0; pos < active_nr; pos++) {
+ struct cache_entry *ce = active_cache[pos];
+ if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
+ if (!ce_stage(ce))
+ continue;
+ if (opts->force) {
+ warning("path '%s' is unmerged", ce->name);
+ } else if (stage) {
+ errs |= check_stage(stage, ce, pos);
+ } else if (opts->merge) {
+ errs |= check_all_stages(ce, pos);
+ } else {
+ errs = 1;
+ error("path '%s' is unmerged", ce->name);
+ }
+ pos = skip_same_name(ce, pos) - 1;
+ }
+ }
+ if (errs)
+ return 1;
+
+ /* Now we are committed to check them out */
+ memset(&state, 0, sizeof(state));
+ state.force = 1;
+ state.refresh_cache = 1;
+ for (pos = 0; pos < active_nr; pos++) {
+ struct cache_entry *ce = active_cache[pos];
+ if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
+ if (!ce_stage(ce)) {
+ errs |= checkout_entry(ce, &state, NULL);
+ continue;
+ }
+ if (stage)
+ errs |= checkout_stage(stage, ce, pos, &state);
+ else if (merge)
+ errs |= checkout_merged(pos, &state);
+ pos = skip_same_name(ce, pos) - 1;
+ }
+ }
+
+ if (write_cache(newfd, active_cache, active_nr) ||
+ commit_locked_index(lock_file))
+ die("unable to write new index file");
+
+ resolve_ref("HEAD", rev, 0, &flag);
+ head = lookup_commit_reference_gently(rev, 1);
+
+ errs |= post_checkout_hook(head, head, 0);
+ return errs;
+}
+
+static void show_local_changes(struct object *head)
+{
+ struct rev_info rev;
+ /* I think we want full paths, even if we're in a subdirectory. */
+ init_revisions(&rev, NULL);
+ rev.abbrev = 0;
+ rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
+ if (diff_setup_done(&rev.diffopt) < 0)
+ die("diff_setup_done failed");
+ add_pending_object(&rev, head, NULL);
+ run_diff_index(&rev, 0);
+}
+
+static void describe_detached_head(char *msg, struct commit *commit)
+{
+ struct strbuf sb = STRBUF_INIT;
+ struct pretty_print_context ctx = {0};
+ parse_commit(commit);
+ pretty_print_commit(CMIT_FMT_ONELINE, commit, &sb, &ctx);
+ fprintf(stderr, "%s %s... %s\n", msg,
+ find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
+ strbuf_release(&sb);
+}
+
+static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
+{
+ struct unpack_trees_options opts;
+ struct tree_desc tree_desc;
+
+ memset(&opts, 0, sizeof(opts));
+ opts.head_idx = -1;
+ opts.update = worktree;
+ opts.skip_unmerged = !worktree;
+ opts.reset = 1;
+ opts.merge = 1;
+ opts.fn = oneway_merge;
+ opts.verbose_update = !o->quiet;
+ opts.src_index = &the_index;
+ opts.dst_index = &the_index;
+ parse_tree(tree);
+ init_tree_desc(&tree_desc, tree->buffer, tree->size);
+ switch (unpack_trees(1, &tree_desc, &opts)) {
+ case -2:
+ o->writeout_error = 1;
+ /*
+ * We return 0 nevertheless, as the index is all right
+ * and more importantly we have made best efforts to
+ * update paths in the work tree, and we cannot revert
+ * them.
+ */
+ case 0:
+ return 0;
+ default:
+ return 128;
+ }
+}
+
+struct branch_info {
+ const char *name; /* The short name used */
+ const char *path; /* The full name of a real branch */
+ struct commit *commit; /* The named commit */
+};
+
+static void setup_branch_path(struct branch_info *branch)
+{
+ struct strbuf buf = STRBUF_INIT;
+
+ strbuf_branchname(&buf, branch->name);
+ if (strcmp(buf.buf, branch->name))
+ branch->name = xstrdup(buf.buf);
+ strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
+ branch->path = strbuf_detach(&buf, NULL);
+}
+
+static int merge_working_tree(struct checkout_opts *opts,
+ struct branch_info *old, struct branch_info *new)
+{
+ int ret;
+ struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
+ int newfd = hold_locked_index(lock_file, 1);
+
+ if (read_cache_preload(NULL) < 0)
+ return error("corrupt index file");
+
+ resolve_undo_clear();
+ if (opts->force) {
+ ret = reset_tree(new->commit->tree, opts, 1);
+ if (ret)
+ return ret;
+ } else {
+ struct tree_desc trees[2];
+ struct tree *tree;
+ struct unpack_trees_options topts;
+
+ memset(&topts, 0, sizeof(topts));
+ topts.head_idx = -1;
+ topts.src_index = &the_index;
+ topts.dst_index = &the_index;
+
+ topts.msgs.not_uptodate_file = "You have local changes to '%s'; cannot switch branches.";
+
+ refresh_cache(REFRESH_QUIET);
+
+ if (unmerged_cache()) {
+ error("you need to resolve your current index first");
+ return 1;
+ }
+
+ /* 2-way merge to the new branch */
+ topts.initial_checkout = is_cache_unborn();
+ topts.update = 1;
+ topts.merge = 1;
+ topts.gently = opts->merge && old->commit;
+ topts.verbose_update = !opts->quiet;
+ topts.fn = twoway_merge;
+ topts.dir = xcalloc(1, sizeof(*topts.dir));
+ topts.dir->flags |= DIR_SHOW_IGNORED;
+ topts.dir->exclude_per_dir = ".gitignore";
+ tree = parse_tree_indirect(old->commit ?
+ old->commit->object.sha1 :
+ (unsigned char *)EMPTY_TREE_SHA1_BIN);
+ init_tree_desc(&trees[0], tree->buffer, tree->size);
+ tree = parse_tree_indirect(new->commit->object.sha1);
+ init_tree_desc(&trees[1], tree->buffer, tree->size);
+
+ ret = unpack_trees(2, trees, &topts);
+ if (ret == -1) {
+ /*
+ * Unpack couldn't do a trivial merge; either
+ * give up or do a real merge, depending on
+ * whether the merge flag was used.
+ */
+ struct tree *result;
+ struct tree *work;
+ struct merge_options o;
+ if (!opts->merge)
+ return 1;
+
+ /*
+ * Without old->commit, the below is the same as
+ * the two-tree unpack we already tried and failed.
+ */
+ if (!old->commit)
+ return 1;
+
+ /* Do more real merge */
+
+ /*
+ * We update the index fully, then write the
+ * tree from the index, then merge the new
+ * branch with the current tree, with the old
+ * branch as the base. Then we reset the index
+ * (but not the working tree) to the new
+ * branch, leaving the working tree as the
+ * merged version, but skipping unmerged
+ * entries in the index.
+ */
+
+ add_files_to_cache(NULL, NULL, 0);
+ init_merge_options(&o);
+ o.verbosity = 0;
+ work = write_tree_from_memory(&o);
+
+ ret = reset_tree(new->commit->tree, opts, 1);
+ if (ret)
+ return ret;
+ o.branch1 = new->name;
+ o.branch2 = "local";
+ merge_trees(&o, new->commit->tree, work,
+ old->commit->tree, &result);
+ ret = reset_tree(new->commit->tree, opts, 0);
+ if (ret)
+ return ret;
+ }
+ }
+
+ if (write_cache(newfd, active_cache, active_nr) ||
+ commit_locked_index(lock_file))
+ die("unable to write new index file");
+
+ if (!opts->force && !opts->quiet)
+ show_local_changes(&new->commit->object);
+
+ return 0;
+}
+
+static void report_tracking(struct branch_info *new)
+{
+ struct strbuf sb = STRBUF_INIT;
+ struct branch *branch = branch_get(new->name);
+
+ if (!format_tracking_info(branch, &sb))
+ return;
+ fputs(sb.buf, stdout);
+ strbuf_release(&sb);
+}
+
+static void detach_advice(const char *old_path, const char *new_name)
+{
+ const char fmt[] =
+ "Note: checking out '%s'.\n\n"
+ "You are in 'detached HEAD' state. You can look around, make experimental\n"
+ "changes and commit them, and you can discard any commits you make in this\n"
+ "state without impacting any branches by performing another checkout.\n\n"
+ "If you want to create a new branch to retain commits you create, you may\n"
+ "do so (now or later) by using -b with the checkout command again. Example:\n\n"
+ " git checkout -b new_branch_name\n\n";
+
+ fprintf(stderr, fmt, new_name);
+}
+
+static void update_refs_for_switch(struct checkout_opts *opts,
+ struct branch_info *old,
+ struct branch_info *new)
+{
+ struct strbuf msg = STRBUF_INIT;
+ const char *old_desc;
+ if (opts->new_branch) {
+ create_branch(old->name, opts->new_branch, new->name, 0,
+ opts->new_branch_log, opts->track);
+ new->name = opts->new_branch;
+ setup_branch_path(new);
+ }
+
+ old_desc = old->name;
+ if (!old_desc && old->commit)
+ old_desc = sha1_to_hex(old->commit->object.sha1);
+ strbuf_addf(&msg, "checkout: moving from %s to %s",
+ old_desc ? old_desc : "(invalid)", new->name);
+
+ if (new->path) {
+ create_symref("HEAD", new->path, msg.buf);
+ if (!opts->quiet) {
+ if (old->path && !strcmp(new->path, old->path))
+ fprintf(stderr, "Already on '%s'\n",
+ new->name);
+ else
+ fprintf(stderr, "Switched to%s branch '%s'\n",
+ opts->new_branch ? " a new" : "",
+ new->name);
+ }
+ } else if (strcmp(new->name, "HEAD")) {
+ update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
+ REF_NODEREF, DIE_ON_ERR);
+ if (!opts->quiet) {
+ if (old->path && advice_detached_head)
+ detach_advice(old->path, new->name);
+ describe_detached_head("HEAD is now at", new->commit);
+ }
+ }
+ remove_branch_state();
+ strbuf_release(&msg);
+ if (!opts->quiet && (new->path || !strcmp(new->name, "HEAD")))
+ report_tracking(new);
+}
+
+static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
+{
+ int ret = 0;
+ struct branch_info old;
+ unsigned char rev[20];
+ int flag;
+ memset(&old, 0, sizeof(old));
+ old.path = resolve_ref("HEAD", rev, 0, &flag);
+ old.commit = lookup_commit_reference_gently(rev, 1);
+ if (!(flag & REF_ISSYMREF))
+ old.path = NULL;
+
+ if (old.path && !prefixcmp(old.path, "refs/heads/"))
+ old.name = old.path + strlen("refs/heads/");
+
+ if (!new->name) {
+ new->name = "HEAD";
+ new->commit = old.commit;
+ if (!new->commit)
+ die("You are on a branch yet to be born");
+ parse_commit(new->commit);
+ }
+
+ ret = merge_working_tree(opts, &old, new);
+ if (ret)
+ return ret;
+
+ /*
+ * If we were on a detached HEAD, but have now moved to
+ * a new commit, we want to mention the old commit once more
+ * to remind the user that it might be lost.
+ */
+ if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
+ describe_detached_head("Previous HEAD position was", old.commit);
+
+ update_refs_for_switch(opts, &old, new);
+
+ ret = post_checkout_hook(old.commit, new->commit, 1);
+ return ret || opts->writeout_error;
+}
+
+static int git_checkout_config(const char *var, const char *value, void *cb)
+{
+ return git_xmerge_config(var, value, cb);
+}
+
+static int interactive_checkout(const char *revision, const char **pathspec,
+ struct checkout_opts *opts)
+{
+ return run_add_interactive(revision, "--patch=checkout", pathspec);
+}
+
+struct tracking_name_data {
+ const char *name;
+ char *remote;
+ int unique;
+};
+
+static int check_tracking_name(const char *refname, const unsigned char *sha1,
+ int flags, void *cb_data)
+{
+ struct tracking_name_data *cb = cb_data;
+ const char *slash;
+
+ if (prefixcmp(refname, "refs/remotes/"))
+ return 0;
+ slash = strchr(refname + 13, '/');
+ if (!slash || strcmp(slash + 1, cb->name))
+ return 0;
+ if (cb->remote) {
+ cb->unique = 0;
+ return 0;
+ }
+ cb->remote = xstrdup(refname);
+ return 0;
+}
+
+static const char *unique_tracking_name(const char *name)
+{
+ struct tracking_name_data cb_data = { name, NULL, 1 };
+ for_each_ref(check_tracking_name, &cb_data);
+ if (cb_data.unique)
+ return cb_data.remote;
+ free(cb_data.remote);
+ return NULL;
+}
+
+int cmd_checkout(int argc, const char **argv, const char *prefix)
+{
+ struct checkout_opts opts;
+ unsigned char rev[20];
+ const char *arg;
+ struct branch_info new;
+ struct tree *source_tree = NULL;
+ char *conflict_style = NULL;
+ int patch_mode = 0;
+ int dwim_new_local_branch = 1;
+ struct option options[] = {
+ OPT__QUIET(&opts.quiet),
+ OPT_STRING('b', NULL, &opts.new_branch, "new branch", "branch"),
+ OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "log for new branch"),
+ OPT_SET_INT('t', "track", &opts.track, "track",
+ BRANCH_TRACK_EXPLICIT),
+ OPT_SET_INT('2', "ours", &opts.writeout_stage, "stage",
+ 2),
+ OPT_SET_INT('3', "theirs", &opts.writeout_stage, "stage",
+ 3),
+ OPT_BOOLEAN('f', "force", &opts.force, "force"),
+ OPT_BOOLEAN('m', "merge", &opts.merge, "merge"),
+ OPT_STRING(0, "conflict", &conflict_style, "style",
+ "conflict style (merge or diff3)"),
+ OPT_BOOLEAN('p', "patch", &patch_mode, "select hunks interactively"),
+ { OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
+ "second guess 'git checkout no-such-branch'",
+ PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
+ OPT_END(),
+ };
+ int has_dash_dash;
+
+ memset(&opts, 0, sizeof(opts));
+ memset(&new, 0, sizeof(new));
+
+ git_config(git_checkout_config, NULL);
+
+ opts.track = BRANCH_TRACK_UNSPECIFIED;
+
+ argc = parse_options(argc, argv, prefix, options, checkout_usage,
+ PARSE_OPT_KEEP_DASHDASH);
+
+ if (patch_mode && (opts.track > 0 || opts.new_branch
+ || opts.new_branch_log || opts.merge || opts.force))
+ die ("--patch is incompatible with all other options");
+
+ /* --track without -b should DWIM */
+ if (0 < opts.track && !opts.new_branch) {
+ const char *argv0 = argv[0];
+ if (!argc || !strcmp(argv0, "--"))
+ die ("--track needs a branch name");
+ if (!prefixcmp(argv0, "refs/"))
+ argv0 += 5;
+ if (!prefixcmp(argv0, "remotes/"))
+ argv0 += 8;
+ argv0 = strchr(argv0, '/');
+ if (!argv0 || !argv0[1])
+ die ("Missing branch name; try -b");
+ opts.new_branch = argv0 + 1;
+ }
+
+ 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");
+
+ /*
+ * 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. As a special case,
+ * if <something> is A...B (missing A or B means HEAD but you can
+ * omit at most one side), and if there is a unique merge base
+ * between A and B, A...B names that merge base.
+ *
+ * With no paths, if <something> is _not_ a commit, no -t nor -b
+ * was given, and there is a tracking branch whose name is
+ * <something> in one and only one remote, then this is a short-hand
+ * to fork local <something> from that remote tracking branch.
+ *
+ * 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];
+ has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
+
+ if (!strcmp(arg, "-"))
+ arg = "@{-1}";
+
+ if (get_sha1_mb(arg, rev)) {
+ if (has_dash_dash) /* case (1) */
+ die("invalid reference: %s", arg);
+ if (!patch_mode &&
+ dwim_new_local_branch &&
+ opts.track == BRANCH_TRACK_UNSPECIFIED &&
+ !opts.new_branch &&
+ !check_filename(NULL, arg) &&
+ argc == 1) {
+ const char *remote = unique_tracking_name(arg);
+ if (!remote || get_sha1(remote, rev))
+ goto no_reference;
+ opts.new_branch = arg;
+ arg = remote;
+ /* DWIMmed to create local branch */
+ }
+ else
+ goto no_reference;
+ }
+
+ /* we can't end up being in (2) anymore, eat the argument */
+ argv++;
+ argc--;
+
+ new.name = arg;
+ if ((new.commit = lookup_commit_reference_gently(rev, 1))) {
+ setup_branch_path(&new);
+
+ if ((check_ref_format(new.path) == CHECK_REF_FORMAT_OK) &&
+ resolve_ref(new.path, rev, 1, NULL))
+ ;
+ else
+ new.path = NULL;
+ parse_commit(new.commit);
+ source_tree = new.commit->tree;
+ } 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--;
+ }
+ }
+
+no_reference:
+
+ if (opts.track == BRANCH_TRACK_UNSPECIFIED)
+ opts.track = git_branch_track;
+
+ if (argc) {
+ const char **pathspec = get_pathspec(prefix, argv);
+
+ if (!pathspec)
+ die("invalid path specification");
+
+ if (patch_mode)
+ return interactive_checkout(new.name, pathspec, &opts);
+
+ /* 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.");
+ }
+ }
+
+ 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(source_tree, pathspec, &opts);
+ }
+
+ if (patch_mode)
+ return interactive_checkout(new.name, NULL, &opts);
+
+ if (opts.new_branch) {
+ struct strbuf buf = STRBUF_INIT;
+ if (strbuf_check_branch_ref(&buf, opts.new_branch))
+ die("git checkout: we do not like '%s' as a branch name.",
+ opts.new_branch);
+ if (!get_sha1(buf.buf, rev))
+ die("git checkout: branch %s already exists", opts.new_branch);
+ 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.");
+
+ return switch_branches(&opts, &new);
+}