/*
 * Builtin "git branch"
 *
 * Copyright (c) 2006 Kristian Høgsberg <krh@redhat.com>
 * Based on git-branch.sh by Junio C Hamano.
 */

#include "cache.h"
#include "color.h"
#include "refs.h"
#include "commit.h"
#include "builtin.h"
#include "remote.h"
#include "parse-options.h"
#include "branch.h"
#include "diff.h"
#include "revision.h"
#include "string-list.h"
#include "column.h"
#include "utf8.h"
#include "wt-status.h"

static const char * const builtin_branch_usage[] = {
        N_("git branch [<options>] [-r | -a] [--merged | --no-merged]"),
        N_("git branch [<options>] [-l] [-f] <branch-name> [<start-point>]"),
        N_("git branch [<options>] [-r] (-d | -D) <branch-name>..."),
        N_("git branch [<options>] (-m | -M) [<old-branch>] <new-branch>"),
        NULL
};

#define REF_LOCAL_BRANCH    0x01
#define REF_REMOTE_BRANCH   0x02

static const char *head;
static unsigned char head_sha1[20];

static int branch_use_color = -1;
static char branch_colors[][COLOR_MAXLEN] = {
        GIT_COLOR_RESET,
        GIT_COLOR_NORMAL,       /* PLAIN */
        GIT_COLOR_RED,          /* REMOTE */
        GIT_COLOR_NORMAL,       /* LOCAL */
        GIT_COLOR_GREEN,        /* CURRENT */
        GIT_COLOR_BLUE,         /* UPSTREAM */
};
enum color_branch {
        BRANCH_COLOR_RESET = 0,
        BRANCH_COLOR_PLAIN = 1,
        BRANCH_COLOR_REMOTE = 2,
        BRANCH_COLOR_LOCAL = 3,
        BRANCH_COLOR_CURRENT = 4,
        BRANCH_COLOR_UPSTREAM = 5
};

static enum merge_filter {
        NO_FILTER = 0,
        SHOW_NOT_MERGED,
        SHOW_MERGED
} merge_filter;
static unsigned char merge_filter_ref[20];

static struct string_list output = STRING_LIST_INIT_DUP;
static unsigned int colopts;

static int parse_branch_color_slot(const char *slot)
{
        if (!strcasecmp(slot, "plain"))
                return BRANCH_COLOR_PLAIN;
        if (!strcasecmp(slot, "reset"))
                return BRANCH_COLOR_RESET;
        if (!strcasecmp(slot, "remote"))
                return BRANCH_COLOR_REMOTE;
        if (!strcasecmp(slot, "local"))
                return BRANCH_COLOR_LOCAL;
        if (!strcasecmp(slot, "current"))
                return BRANCH_COLOR_CURRENT;
        if (!strcasecmp(slot, "upstream"))
                return BRANCH_COLOR_UPSTREAM;
        return -1;
}

static int git_branch_config(const char *var, const char *value, void *cb)
{
        const char *slot_name;

        if (starts_with(var, "column."))
                return git_column_config(var, value, "branch", &colopts);
        if (!strcmp(var, "color.branch")) {
                branch_use_color = git_config_colorbool(var, value);
                return 0;
        }
        if (skip_prefix(var, "color.branch.", &slot_name)) {
                int slot = parse_branch_color_slot(slot_name);
                if (slot < 0)
                        return 0;
                if (!value)
                        return config_error_nonbool(var);
                return color_parse(value, branch_colors[slot]);
        }
        return git_color_default_config(var, value, cb);
}

static const char *branch_get_color(enum color_branch ix)
{
        if (want_color(branch_use_color))
                return branch_colors[ix];
        return "";
}

static int branch_merged(int kind, const char *name,
                         struct commit *rev, struct commit *head_rev)
{
        /*
         * This checks whether the merge bases of branch and HEAD (or
         * the other branch this branch builds upon) contains the
         * branch, which means that the branch has already been merged
         * safely to HEAD (or the other branch).
         */
        struct commit *reference_rev = NULL;
        const char *reference_name = NULL;
        void *reference_name_to_free = NULL;
        int merged;

        if (kind == REF_LOCAL_BRANCH) {
                struct branch *branch = branch_get(name);
                const char *upstream = branch_get_upstream(branch, NULL);
                unsigned char sha1[20];

                if (upstream &&
                    (reference_name = reference_name_to_free =
                     resolve_refdup(upstream, RESOLVE_REF_READING,
                                    sha1, NULL)) != NULL)
                        reference_rev = lookup_commit_reference(sha1);
        }
        if (!reference_rev)
                reference_rev = head_rev;

        merged = in_merge_bases(rev, reference_rev);

        /*
         * After the safety valve is fully redefined to "check with
         * upstream, if any, otherwise with HEAD", we should just
         * return the result of the in_merge_bases() above without
         * any of the following code, but during the transition period,
         * a gentle reminder is in order.
         */
        if ((head_rev != reference_rev) &&
            in_merge_bases(rev, head_rev) != merged) {
                if (merged)
                        warning(_("deleting branch '%s' that has been merged to\n"
                                "         '%s', but not yet merged to HEAD."),
                                name, reference_name);
                else
                        warning(_("not deleting branch '%s' that is not yet merged to\n"
                                "         '%s', even though it is merged to HEAD."),
                                name, reference_name);
        }
        free(reference_name_to_free);
        return merged;
}

static int check_branch_commit(const char *branchname, const char *refname,
                               const unsigned char *sha1, struct commit *head_rev,
                               int kinds, int force)
{
        struct commit *rev = lookup_commit_reference(sha1);
        if (!rev) {
                error(_("Couldn't look up commit object for '%s'"), refname);
                return -1;
        }
        if (!force && !branch_merged(kinds, branchname, rev, head_rev)) {
                error(_("The branch '%s' is not fully merged.\n"
                      "If you are sure you want to delete it, "
                      "run 'git branch -D %s'."), branchname, branchname);
                return -1;
        }
        return 0;
}

static void delete_branch_config(const char *branchname)
{
        struct strbuf buf = STRBUF_INIT;
        strbuf_addf(&buf, "branch.%s", branchname);
        if (git_config_rename_section(buf.buf, NULL) < 0)
                warning(_("Update of config-file failed"));
        strbuf_release(&buf);
}

static int delete_branches(int argc, const char **argv, int force, int kinds,
                           int quiet)
{
        struct commit *head_rev = NULL;
        unsigned char sha1[20];
        char *name = NULL;
        const char *fmt;
        int i;
        int ret = 0;
        int remote_branch = 0;
        struct strbuf bname = STRBUF_INIT;

        switch (kinds) {
        case REF_REMOTE_BRANCH:
                fmt = "refs/remotes/%s";
                /* For subsequent UI messages */
                remote_branch = 1;

                force = 1;
                break;
        case REF_LOCAL_BRANCH:
                fmt = "refs/heads/%s";
                break;
        default:
                die(_("cannot use -a with -d"));
        }

        if (!force) {
                head_rev = lookup_commit_reference(head_sha1);
                if (!head_rev)
                        die(_("Couldn't look up commit object for HEAD"));
        }
        for (i = 0; i < argc; i++, strbuf_release(&bname)) {
                const char *target;
                int flags = 0;

                strbuf_branchname(&bname, argv[i]);
                if (kinds == REF_LOCAL_BRANCH && !strcmp(head, bname.buf)) {
                        error(_("Cannot delete the branch '%s' "
                              "which you are currently on."), bname.buf);
                        ret = 1;
                        continue;
                }

                free(name);

                name = mkpathdup(fmt, bname.buf);
                target = resolve_ref_unsafe(name,
                                            RESOLVE_REF_READING
                                            | RESOLVE_REF_NO_RECURSE
                                            | RESOLVE_REF_ALLOW_BAD_NAME,
                                            sha1, &flags);
                if (!target) {
                        error(remote_branch
                              ? _("remote-tracking branch '%s' not found.")
                              : _("branch '%s' not found."), bname.buf);
                        ret = 1;
                        continue;
                }

                if (!(flags & (REF_ISSYMREF|REF_ISBROKEN)) &&
                    check_branch_commit(bname.buf, name, sha1, head_rev, kinds,
                                        force)) {
                        ret = 1;
                        continue;
                }

                if (delete_ref(name, is_null_sha1(sha1) ? NULL : sha1,
                               REF_NODEREF)) {
                        error(remote_branch
                              ? _("Error deleting remote-tracking branch '%s'")
                              : _("Error deleting branch '%s'"),
                              bname.buf);
                        ret = 1;
                        continue;
                }
                if (!quiet) {
                        printf(remote_branch
                               ? _("Deleted remote-tracking branch %s (was %s).\n")
                               : _("Deleted branch %s (was %s).\n"),
                               bname.buf,
                               (flags & REF_ISBROKEN) ? "broken"
                               : (flags & REF_ISSYMREF) ? target
                               : find_unique_abbrev(sha1, DEFAULT_ABBREV));
                }
                delete_branch_config(bname.buf);
        }

        free(name);

        return(ret);
}

struct ref_item {
        char *name;
        char *dest;
        unsigned int kind, width;
        struct commit *commit;
        int ignore;
};

struct ref_list {
        struct rev_info revs;
        int index, alloc, maxwidth, verbose, abbrev;
        struct ref_item *list;
        struct commit_list *with_commit;
        int kinds;
};

static char *resolve_symref(const char *src, const char *prefix)
{
        unsigned char sha1[20];
        int flag;
        const char *dst;

        dst = resolve_ref_unsafe(src, 0, sha1, &flag);
        if (!(dst && (flag & REF_ISSYMREF)))
                return NULL;
        if (prefix)
                skip_prefix(dst, prefix, &dst);
        return xstrdup(dst);
}

struct append_ref_cb {
        struct ref_list *ref_list;
        const char **pattern;
        int ret;
};

static int match_patterns(const char **pattern, const char *refname)
{
        if (!*pattern)
                return 1; /* no pattern always matches */
        while (*pattern) {
                if (!wildmatch(*pattern, refname, 0, NULL))
                        return 1;
                pattern++;
        }
        return 0;
}

static int append_ref(const char *refname, const struct object_id *oid, int flags, void *cb_data)
{
        struct append_ref_cb *cb = (struct append_ref_cb *)(cb_data);
        struct ref_list *ref_list = cb->ref_list;
        struct ref_item *newitem;
        struct commit *commit;
        int kind, i;
        const char *prefix, *orig_refname = refname;

        static struct {
                int kind;
                const char *prefix;
        } ref_kind[] = {
                { REF_LOCAL_BRANCH, "refs/heads/" },
                { REF_REMOTE_BRANCH, "refs/remotes/" },
        };

        /* Detect kind */
        for (i = 0; i < ARRAY_SIZE(ref_kind); i++) {
                prefix = ref_kind[i].prefix;
                if (skip_prefix(refname, prefix, &refname)) {
                        kind = ref_kind[i].kind;
                        break;
                }
        }
        if (ARRAY_SIZE(ref_kind) <= i)
                return 0;

        /* Don't add types the caller doesn't want */
        if ((kind & ref_list->kinds) == 0)
                return 0;

        if (!match_patterns(cb->pattern, refname))
                return 0;

        commit = NULL;
        if (ref_list->verbose || ref_list->with_commit || merge_filter != NO_FILTER) {
                commit = lookup_commit_reference_gently(oid->hash, 1);
                if (!commit) {
                        cb->ret = error(_("branch '%s' does not point at a commit"), refname);
                        return 0;
                }

                /* Filter with with_commit if specified */
                if (!is_descendant_of(commit, ref_list->with_commit))
                        return 0;

                if (merge_filter != NO_FILTER)
                        add_pending_object(&ref_list->revs,
                                           (struct object *)commit, refname);
        }

        ALLOC_GROW(ref_list->list, ref_list->index + 1, ref_list->alloc);

        /* Record the new item */
        newitem = &(ref_list->list[ref_list->index++]);
        newitem->name = xstrdup(refname);
        newitem->kind = kind;
        newitem->commit = commit;
        newitem->width = utf8_strwidth(refname);
        newitem->dest = resolve_symref(orig_refname, prefix);
        newitem->ignore = 0;
        /* adjust for "remotes/" */
        if (newitem->kind == REF_REMOTE_BRANCH &&
            ref_list->kinds != REF_REMOTE_BRANCH)
                newitem->width += 8;
        if (newitem->width > ref_list->maxwidth)
                ref_list->maxwidth = newitem->width;

        return 0;
}

static void free_ref_list(struct ref_list *ref_list)
{
        int i;

        for (i = 0; i < ref_list->index; i++) {
                free(ref_list->list[i].name);
                free(ref_list->list[i].dest);
        }
        free(ref_list->list);
}

static int ref_cmp(const void *r1, const void *r2)
{
        struct ref_item *c1 = (struct ref_item *)(r1);
        struct ref_item *c2 = (struct ref_item *)(r2);

        if (c1->kind != c2->kind)
                return c1->kind - c2->kind;
        return strcmp(c1->name, c2->name);
}

static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
                int show_upstream_ref)
{
        int ours, theirs;
        char *ref = NULL;
        struct branch *branch = branch_get(branch_name);
        const char *upstream;
        struct strbuf fancy = STRBUF_INIT;
        int upstream_is_gone = 0;
        int added_decoration = 1;

        if (stat_tracking_info(branch, &ours, &theirs, &upstream) < 0) {
                if (!upstream)
                        return;
                upstream_is_gone = 1;
        }

        if (show_upstream_ref) {
                ref = shorten_unambiguous_ref(upstream, 0);
                if (want_color(branch_use_color))
                        strbuf_addf(&fancy, "%s%s%s",
                                        branch_get_color(BRANCH_COLOR_UPSTREAM),
                                        ref, branch_get_color(BRANCH_COLOR_RESET));
                else
                        strbuf_addstr(&fancy, ref);
        }

        if (upstream_is_gone) {
                if (show_upstream_ref)
                        strbuf_addf(stat, _("[%s: gone]"), fancy.buf);
                else
                        added_decoration = 0;
        } else if (!ours && !theirs) {
                if (show_upstream_ref)
                        strbuf_addf(stat, _("[%s]"), fancy.buf);
                else
                        added_decoration = 0;
        } else if (!ours) {
                if (show_upstream_ref)
                        strbuf_addf(stat, _("[%s: behind %d]"), fancy.buf, theirs);
                else
                        strbuf_addf(stat, _("[behind %d]"), theirs);

        } else if (!theirs) {
                if (show_upstream_ref)
                        strbuf_addf(stat, _("[%s: ahead %d]"), fancy.buf, ours);
                else
                        strbuf_addf(stat, _("[ahead %d]"), ours);
        } else {
                if (show_upstream_ref)
                        strbuf_addf(stat, _("[%s: ahead %d, behind %d]"),
                                    fancy.buf, ours, theirs);
                else
                        strbuf_addf(stat, _("[ahead %d, behind %d]"),
                                    ours, theirs);
        }
        strbuf_release(&fancy);
        if (added_decoration)
                strbuf_addch(stat, ' ');
        free(ref);
}

static void add_verbose_info(struct strbuf *out, struct ref_item *item,
                             int verbose, int abbrev)
{
        struct strbuf subject = STRBUF_INIT, stat = STRBUF_INIT;
        const char *sub = _(" **** invalid ref ****");
        struct commit *commit = item->commit;

        if (!parse_commit(commit)) {
                pp_commit_easy(CMIT_FMT_ONELINE, commit, &subject);
                sub = subject.buf;
        }

        if (item->kind == REF_LOCAL_BRANCH)
                fill_tracking_info(&stat, item->name, verbose > 1);

        strbuf_addf(out, " %s %s%s",
                find_unique_abbrev(item->commit->object.sha1, abbrev),
                stat.buf, sub);
        strbuf_release(&stat);
        strbuf_release(&subject);
}

static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
                           int abbrev, int current, char *prefix)
{
        char c;
        int color;
        struct strbuf out = STRBUF_INIT, name = STRBUF_INIT;

        if (item->ignore)
                return;

        switch (item->kind) {
        case REF_LOCAL_BRANCH:
                color = BRANCH_COLOR_LOCAL;
                break;
        case REF_REMOTE_BRANCH:
                color = BRANCH_COLOR_REMOTE;
                break;
        default:
                color = BRANCH_COLOR_PLAIN;
                break;
        }

        c = ' ';
        if (current) {
                c = '*';
                color = BRANCH_COLOR_CURRENT;
        }

        strbuf_addf(&name, "%s%s", prefix, item->name);
        if (verbose) {
                int utf8_compensation = strlen(name.buf) - utf8_strwidth(name.buf);
                strbuf_addf(&out, "%c %s%-*s%s", c, branch_get_color(color),
                            maxwidth + utf8_compensation, name.buf,
                            branch_get_color(BRANCH_COLOR_RESET));
        } else
                strbuf_addf(&out, "%c %s%s%s", c, branch_get_color(color),
                            name.buf, branch_get_color(BRANCH_COLOR_RESET));

        if (item->dest)
                strbuf_addf(&out, " -> %s", item->dest);
        else if (verbose)
                /* " f7c0c00 [ahead 58, behind 197] vcs-svn: drop obj_pool.h" */
                add_verbose_info(&out, item, verbose, abbrev);
        if (column_active(colopts)) {
                assert(!verbose && "--column and --verbose are incompatible");
                string_list_append(&output, out.buf);
        } else {
                printf("%s\n", out.buf);
        }
        strbuf_release(&name);
        strbuf_release(&out);
}

static int calc_maxwidth(struct ref_list *refs)
{
        int i, w = 0;
        for (i = 0; i < refs->index; i++) {
                if (refs->list[i].ignore)
                        continue;
                if (refs->list[i].width > w)
                        w = refs->list[i].width;
        }
        return w;
}

static char *get_head_description(void)
{
        struct strbuf desc = STRBUF_INIT;
        struct wt_status_state state;
        memset(&state, 0, sizeof(state));
        wt_status_get_state(&state, 1);
        if (state.rebase_in_progress ||
            state.rebase_interactive_in_progress)
                strbuf_addf(&desc, _("(no branch, rebasing %s)"),
                            state.branch);
        else if (state.bisect_in_progress)
                strbuf_addf(&desc, _("(no branch, bisect started on %s)"),
                            state.branch);
        else if (state.detached_from) {
                /* TRANSLATORS: make sure these match _("HEAD detached at ")
                   and _("HEAD detached from ") in wt-status.c */
                if (state.detached_at)
                        strbuf_addf(&desc, _("(HEAD detached at %s)"),
                                state.detached_from);
                else
                        strbuf_addf(&desc, _("(HEAD detached from %s)"),
                                state.detached_from);
        }
        else
                strbuf_addstr(&desc, _("(no branch)"));
        free(state.branch);
        free(state.onto);
        free(state.detached_from);
        return strbuf_detach(&desc, NULL);
}

static void show_detached(struct ref_list *ref_list)
{
        struct commit *head_commit = lookup_commit_reference_gently(head_sha1, 1);

        if (head_commit && is_descendant_of(head_commit, ref_list->with_commit)) {
                struct ref_item item;
                item.name = get_head_description();
                item.width = utf8_strwidth(item.name);
                item.kind = REF_LOCAL_BRANCH;
                item.dest = NULL;
                item.commit = head_commit;
                item.ignore = 0;
                if (item.width > ref_list->maxwidth)
                        ref_list->maxwidth = item.width;
                print_ref_item(&item, ref_list->maxwidth, ref_list->verbose, ref_list->abbrev, 1, "");
                free(item.name);
        }
}

static int print_ref_list(int kinds, int detached, int verbose, int abbrev, struct commit_list *with_commit, const char **pattern)
{
        int i;
        struct append_ref_cb cb;
        struct ref_list ref_list;

        memset(&ref_list, 0, sizeof(ref_list));
        ref_list.kinds = kinds;
        ref_list.verbose = verbose;
        ref_list.abbrev = abbrev;
        ref_list.with_commit = with_commit;
        if (merge_filter != NO_FILTER)
                init_revisions(&ref_list.revs, NULL);
        cb.ref_list = &ref_list;
        cb.pattern = pattern;
        cb.ret = 0;
        for_each_rawref(append_ref, &cb);
        if (merge_filter != NO_FILTER) {
                struct commit *filter;
                filter = lookup_commit_reference_gently(merge_filter_ref, 0);
                if (!filter)
                        die(_("object '%s' does not point to a commit"),
                            sha1_to_hex(merge_filter_ref));

                filter->object.flags |= UNINTERESTING;
                add_pending_object(&ref_list.revs,
                                   (struct object *) filter, "");
                ref_list.revs.limited = 1;

                if (prepare_revision_walk(&ref_list.revs))
                        die(_("revision walk setup failed"));

                for (i = 0; i < ref_list.index; i++) {
                        struct ref_item *item = &ref_list.list[i];
                        struct commit *commit = item->commit;
                        int is_merged = !!(commit->object.flags & UNINTERESTING);
                        item->ignore = is_merged != (merge_filter == SHOW_MERGED);
                }

                for (i = 0; i < ref_list.index; i++) {
                        struct ref_item *item = &ref_list.list[i];
                        clear_commit_marks(item->commit, ALL_REV_FLAGS);
                }
                clear_commit_marks(filter, ALL_REV_FLAGS);

                if (verbose)
                        ref_list.maxwidth = calc_maxwidth(&ref_list);
        }

        qsort(ref_list.list, ref_list.index, sizeof(struct ref_item), ref_cmp);

        detached = (detached && (kinds & REF_LOCAL_BRANCH));
        if (detached && match_patterns(pattern, "HEAD"))
                show_detached(&ref_list);

        for (i = 0; i < ref_list.index; i++) {
                int current = !detached &&
                        (ref_list.list[i].kind == REF_LOCAL_BRANCH) &&
                        !strcmp(ref_list.list[i].name, head);
                char *prefix = (kinds != REF_REMOTE_BRANCH &&
                                ref_list.list[i].kind == REF_REMOTE_BRANCH)
                                ? "remotes/" : "";
                print_ref_item(&ref_list.list[i], ref_list.maxwidth, verbose,
                               abbrev, current, prefix);
        }

        free_ref_list(&ref_list);

        if (cb.ret)
                error(_("some refs could not be read"));

        return cb.ret;
}

static void rename_branch(const char *oldname, const char *newname, int force)
{
        struct strbuf oldref = STRBUF_INIT, newref = STRBUF_INIT, logmsg = STRBUF_INIT;
        struct strbuf oldsection = STRBUF_INIT, newsection = STRBUF_INIT;
        int recovery = 0;
        int clobber_head_ok;

        if (!oldname)
                die(_("cannot rename the current branch while not on any."));

        if (strbuf_check_branch_ref(&oldref, oldname)) {
                /*
                 * Bad name --- this could be an attempt to rename a
                 * ref that we used to allow to be created by accident.
                 */
                if (ref_exists(oldref.buf))
                        recovery = 1;
                else
                        die(_("Invalid branch name: '%s'"), oldname);
        }

        /*
         * A command like "git branch -M currentbranch currentbranch" cannot
         * cause the worktree to become inconsistent with HEAD, so allow it.
         */
        clobber_head_ok = !strcmp(oldname, newname);

        validate_new_branchname(newname, &newref, force, clobber_head_ok);

        strbuf_addf(&logmsg, "Branch: renamed %s to %s",
                 oldref.buf, newref.buf);

        if (rename_ref(oldref.buf, newref.buf, logmsg.buf))
                die(_("Branch rename failed"));
        strbuf_release(&logmsg);

        if (recovery)
                warning(_("Renamed a misnamed branch '%s' away"), oldref.buf + 11);

        /* no need to pass logmsg here as HEAD didn't really move */
        if (!strcmp(oldname, head) && create_symref("HEAD", newref.buf, NULL))
                die(_("Branch renamed to %s, but HEAD is not updated!"), newname);

        strbuf_addf(&oldsection, "branch.%s", oldref.buf + 11);
        strbuf_release(&oldref);
        strbuf_addf(&newsection, "branch.%s", newref.buf + 11);
        strbuf_release(&newref);
        if (git_config_rename_section(oldsection.buf, newsection.buf) < 0)
                die(_("Branch is renamed, but update of config-file failed"));
        strbuf_release(&oldsection);
        strbuf_release(&newsection);
}

static int opt_parse_merge_filter(const struct option *opt, const char *arg, int unset)
{
        merge_filter = ((opt->long_name[0] == 'n')
                        ? SHOW_NOT_MERGED
                        : SHOW_MERGED);
        if (unset)
                merge_filter = SHOW_NOT_MERGED; /* b/c for --no-merged */
        if (!arg)
                arg = "HEAD";
        if (get_sha1(arg, merge_filter_ref))
                die(_("malformed object name %s"), arg);
        return 0;
}

static const char edit_description[] = "BRANCH_DESCRIPTION";

static int edit_branch_description(const char *branch_name)
{
        int status;
        struct strbuf buf = STRBUF_INIT;
        struct strbuf name = STRBUF_INIT;

        read_branch_desc(&buf, branch_name);
        if (!buf.len || buf.buf[buf.len-1] != '\n')
                strbuf_addch(&buf, '\n');
        strbuf_commented_addf(&buf,
                    "Please edit the description for the branch\n"
                    "  %s\n"
                    "Lines starting with '%c' will be stripped.\n",
                    branch_name, comment_line_char);
        if (write_file_gently(git_path(edit_description), "%s", buf.buf)) {
                strbuf_release(&buf);
                return error(_("could not write branch description template: %s"),
                             strerror(errno));
        }
        strbuf_reset(&buf);
        if (launch_editor(git_path(edit_description), &buf, NULL)) {
                strbuf_release(&buf);
                return -1;
        }
        stripspace(&buf, 1);

        strbuf_addf(&name, "branch.%s.description", branch_name);
        status = git_config_set(name.buf, buf.len ? buf.buf : NULL);
        strbuf_release(&name);
        strbuf_release(&buf);

        return status;
}

int cmd_branch(int argc, const char **argv, const char *prefix)
{
        int delete = 0, rename = 0, force = 0, list = 0;
        int verbose = 0, abbrev = -1, detached = 0;
        int reflog = 0, edit_description = 0;
        int quiet = 0, unset_upstream = 0;
        const char *new_upstream = NULL;
        enum branch_track track;
        int kinds = REF_LOCAL_BRANCH;
        struct commit_list *with_commit = NULL;

        struct option options[] = {
                OPT_GROUP(N_("Generic options")),
                OPT__VERBOSE(&verbose,
                        N_("show hash and subject, give twice for upstream branch")),
                OPT__QUIET(&quiet, N_("suppress informational messages")),
                OPT_SET_INT('t', "track",  &track, N_("set up tracking mode (see git-pull(1))"),
                        BRANCH_TRACK_EXPLICIT),
                OPT_SET_INT( 0, "set-upstream",  &track, N_("change upstream info"),
                        BRANCH_TRACK_OVERRIDE),
                OPT_STRING('u', "set-upstream-to", &new_upstream, "upstream", "change the upstream info"),
                OPT_BOOL(0, "unset-upstream", &unset_upstream, "Unset the upstream info"),
                OPT__COLOR(&branch_use_color, N_("use colored output")),
                OPT_SET_INT('r', "remotes",     &kinds, N_("act on remote-tracking branches"),
                        REF_REMOTE_BRANCH),
                {
                        OPTION_CALLBACK, 0, "contains", &with_commit, N_("commit"),
                        N_("print only branches that contain the commit"),
                        PARSE_OPT_LASTARG_DEFAULT,
                        parse_opt_with_commit, (intptr_t)"HEAD",
                },
                {
                        OPTION_CALLBACK, 0, "with", &with_commit, N_("commit"),
                        N_("print only branches that contain the commit"),
                        PARSE_OPT_HIDDEN | PARSE_OPT_LASTARG_DEFAULT,
                        parse_opt_with_commit, (intptr_t) "HEAD",
                },
                OPT__ABBREV(&abbrev),

                OPT_GROUP(N_("Specific git-branch actions:")),
                OPT_SET_INT('a', "all", &kinds, N_("list both remote-tracking and local branches"),
                        REF_REMOTE_BRANCH | REF_LOCAL_BRANCH),
                OPT_BIT('d', "delete", &delete, N_("delete fully merged branch"), 1),
                OPT_BIT('D', NULL, &delete, N_("delete branch (even if not merged)"), 2),
                OPT_BIT('m', "move", &rename, N_("move/rename a branch and its reflog"), 1),
                OPT_BIT('M', NULL, &rename, N_("move/rename a branch, even if target exists"), 2),
                OPT_BOOL(0, "list", &list, N_("list branch names")),
                OPT_BOOL('l', "create-reflog", &reflog, N_("create the branch's reflog")),
                OPT_BOOL(0, "edit-description", &edit_description,
                         N_("edit the description for the branch")),
                OPT__FORCE(&force, N_("force creation, move/rename, deletion")),
                {
                        OPTION_CALLBACK, 0, "no-merged", &merge_filter_ref,
                        N_("commit"), N_("print only not merged branches"),
                        PARSE_OPT_LASTARG_DEFAULT | PARSE_OPT_NONEG,
                        opt_parse_merge_filter, (intptr_t) "HEAD",
                },
                {
                        OPTION_CALLBACK, 0, "merged", &merge_filter_ref,
                        N_("commit"), N_("print only merged branches"),
                        PARSE_OPT_LASTARG_DEFAULT | PARSE_OPT_NONEG,
                        opt_parse_merge_filter, (intptr_t) "HEAD",
                },
                OPT_COLUMN(0, "column", &colopts, N_("list branches in columns")),
                OPT_END(),
        };

        if (argc == 2 && !strcmp(argv[1], "-h"))
                usage_with_options(builtin_branch_usage, options);

        git_config(git_branch_config, NULL);

        track = git_branch_track;

        head = resolve_refdup("HEAD", 0, head_sha1, NULL);
        if (!head)
                die(_("Failed to resolve HEAD as a valid ref."));
        if (!strcmp(head, "HEAD"))
                detached = 1;
        else if (!skip_prefix(head, "refs/heads/", &head))
                die(_("HEAD not found below refs/heads!"));
        hashcpy(merge_filter_ref, head_sha1);


        argc = parse_options(argc, argv, prefix, options, builtin_branch_usage,
                             0);

        if (!delete && !rename && !edit_description && !new_upstream && !unset_upstream && argc == 0)
                list = 1;

        if (with_commit || merge_filter != NO_FILTER)
                list = 1;

        if (!!delete + !!rename + !!new_upstream +
            list + unset_upstream > 1)
                usage_with_options(builtin_branch_usage, options);

        if (abbrev == -1)
                abbrev = DEFAULT_ABBREV;
        finalize_colopts(&colopts, -1);
        if (verbose) {
                if (explicitly_enable_column(colopts))
                        die(_("--column and --verbose are incompatible"));
                colopts = 0;
        }

        if (force) {
                delete *= 2;
                rename *= 2;
        }

        if (delete) {
                if (!argc)
                        die(_("branch name required"));
                return delete_branches(argc, argv, delete > 1, kinds, quiet);
        } else if (list) {
                int ret = print_ref_list(kinds, detached, verbose, abbrev,
                                         with_commit, argv);
                print_columns(&output, colopts, NULL);
                string_list_clear(&output, 0);
                return ret;
        }
        else if (edit_description) {
                const char *branch_name;
                struct strbuf branch_ref = STRBUF_INIT;

                if (!argc) {
                        if (detached)
                                die(_("Cannot give description to detached HEAD"));
                        branch_name = head;
                } else if (argc == 1)
                        branch_name = argv[0];
                else
                        die(_("cannot edit description of more than one branch"));

                strbuf_addf(&branch_ref, "refs/heads/%s", branch_name);
                if (!ref_exists(branch_ref.buf)) {
                        strbuf_release(&branch_ref);

                        if (!argc)
                                return error(_("No commit on branch '%s' yet."),
                                             branch_name);
                        else
                                return error(_("No branch named '%s'."),
                                             branch_name);
                }
                strbuf_release(&branch_ref);

                if (edit_branch_description(branch_name))
                        return 1;
        } else if (rename) {
                if (!argc)
                        die(_("branch name required"));
                else if (argc == 1)
                        rename_branch(head, argv[0], rename > 1);
                else if (argc == 2)
                        rename_branch(argv[0], argv[1], rename > 1);
                else
                        die(_("too many branches for a rename operation"));
        } else if (new_upstream) {
                struct branch *branch = branch_get(argv[0]);

                if (argc > 1)
                        die(_("too many branches to set new upstream"));

                if (!branch) {
                        if (!argc || !strcmp(argv[0], "HEAD"))
                                die(_("could not set upstream of HEAD to %s when "
                                      "it does not point to any branch."),
                                    new_upstream);
                        die(_("no such branch '%s'"), argv[0]);
                }

                if (!ref_exists(branch->refname))
                        die(_("branch '%s' does not exist"), branch->name);

                /*
                 * create_branch takes care of setting up the tracking
                 * info and making sure new_upstream is correct
                 */
                create_branch(head, branch->name, new_upstream, 0, 0, 0, quiet, BRANCH_TRACK_OVERRIDE);
        } else if (unset_upstream) {
                struct branch *branch = branch_get(argv[0]);
                struct strbuf buf = STRBUF_INIT;

                if (argc > 1)
                        die(_("too many branches to unset upstream"));

                if (!branch) {
                        if (!argc || !strcmp(argv[0], "HEAD"))
                                die(_("could not unset upstream of HEAD when "
                                      "it does not point to any branch."));
                        die(_("no such branch '%s'"), argv[0]);
                }

                if (!branch_has_merge_config(branch))
                        die(_("Branch '%s' has no upstream information"), branch->name);

                strbuf_addf(&buf, "branch.%s.remote", branch->name);
                git_config_set_multivar(buf.buf, NULL, NULL, 1);
                strbuf_reset(&buf);
                strbuf_addf(&buf, "branch.%s.merge", branch->name);
                git_config_set_multivar(buf.buf, NULL, NULL, 1);
                strbuf_release(&buf);
        } else if (argc > 0 && argc <= 2) {
                struct branch *branch = branch_get(argv[0]);
                int branch_existed = 0, remote_tracking = 0;
                struct strbuf buf = STRBUF_INIT;

                if (!strcmp(argv[0], "HEAD"))
                        die(_("it does not make sense to create 'HEAD' manually"));

                if (!branch)
                        die(_("no such branch '%s'"), argv[0]);

                if (kinds != REF_LOCAL_BRANCH)
                        die(_("-a and -r options to 'git branch' do not make sense with a branch name"));

                if (track == BRANCH_TRACK_OVERRIDE)
                        fprintf(stderr, _("The --set-upstream flag is deprecated and will be removed. Consider using --track or --set-upstream-to\n"));

                strbuf_addf(&buf, "refs/remotes/%s", branch->name);
                remote_tracking = ref_exists(buf.buf);
                strbuf_release(&buf);

                branch_existed = ref_exists(branch->refname);
                create_branch(head, argv[0], (argc == 2) ? argv[1] : head,
                              force, reflog, 0, quiet, track);

                /*
                 * We only show the instructions if the user gave us
                 * one branch which doesn't exist locally, but is the
                 * name of a remote-tracking branch.
                 */
                if (argc == 1 && track == BRANCH_TRACK_OVERRIDE &&
                    !branch_existed && remote_tracking) {
                        fprintf(stderr, _("\nIf you wanted to make '%s' track '%s', do this:\n\n"), head, branch->name);
                        fprintf(stderr, _("    git branch -d %s\n"), branch->name);
                        fprintf(stderr, _("    git branch --set-upstream-to %s\n"), branch->name);
                }

        } else
                usage_with_options(builtin_branch_usage, options);

        return 0;
}