/*
 * Builtin "git pull"
 *
 * Based on git-pull.sh by Junio C Hamano
 *
 * Fetch one or more remote refs and merge it/them into the current HEAD.
 */
#include "cache.h"
#include "builtin.h"
#include "parse-options.h"
#include "exec_cmd.h"
#include "run-command.h"
#include "sha1-array.h"
#include "remote.h"

static const char * const pull_usage[] = {
        N_("git pull [options] [<repository> [<refspec>...]]"),
        NULL
};

/* Shared options */
static int opt_verbosity;
static char *opt_progress;

/* Options passed to git-merge */
static char *opt_diffstat;
static char *opt_log;
static char *opt_squash;
static char *opt_commit;
static char *opt_edit;
static char *opt_ff;
static char *opt_verify_signatures;
static struct argv_array opt_strategies = ARGV_ARRAY_INIT;
static struct argv_array opt_strategy_opts = ARGV_ARRAY_INIT;
static char *opt_gpg_sign;

/* Options passed to git-fetch */
static char *opt_all;
static char *opt_append;
static char *opt_upload_pack;
static int opt_force;
static char *opt_tags;
static char *opt_prune;
static char *opt_recurse_submodules;
static int opt_dry_run;
static char *opt_keep;
static char *opt_depth;
static char *opt_unshallow;
static char *opt_update_shallow;
static char *opt_refmap;

static struct option pull_options[] = {
        /* Shared options */
        OPT__VERBOSITY(&opt_verbosity),
        OPT_PASSTHRU(0, "progress", &opt_progress, NULL,
                N_("force progress reporting"),
                PARSE_OPT_NOARG),

        /* Options passed to git-merge */
        OPT_GROUP(N_("Options related to merging")),
        OPT_PASSTHRU('n', NULL, &opt_diffstat, NULL,
                N_("do not show a diffstat at the end of the merge"),
                PARSE_OPT_NOARG | PARSE_OPT_NONEG),
        OPT_PASSTHRU(0, "stat", &opt_diffstat, NULL,
                N_("show a diffstat at the end of the merge"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "summary", &opt_diffstat, NULL,
                N_("(synonym to --stat)"),
                PARSE_OPT_NOARG | PARSE_OPT_HIDDEN),
        OPT_PASSTHRU(0, "log", &opt_log, N_("n"),
                N_("add (at most <n>) entries from shortlog to merge commit message"),
                PARSE_OPT_OPTARG),
        OPT_PASSTHRU(0, "squash", &opt_squash, NULL,
                N_("create a single commit instead of doing a merge"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "commit", &opt_commit, NULL,
                N_("perform a commit if the merge succeeds (default)"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "edit", &opt_edit, NULL,
                N_("edit message before committing"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "ff", &opt_ff, NULL,
                N_("allow fast-forward"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "ff-only", &opt_ff, NULL,
                N_("abort if fast-forward is not possible"),
                PARSE_OPT_NOARG | PARSE_OPT_NONEG),
        OPT_PASSTHRU(0, "verify-signatures", &opt_verify_signatures, NULL,
                N_("verify that the named commit has a valid GPG signature"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU_ARGV('s', "strategy", &opt_strategies, N_("strategy"),
                N_("merge strategy to use"),
                0),
        OPT_PASSTHRU_ARGV('X', "strategy-option", &opt_strategy_opts,
                N_("option=value"),
                N_("option for selected merge strategy"),
                0),
        OPT_PASSTHRU('S', "gpg-sign", &opt_gpg_sign, N_("key-id"),
                N_("GPG sign commit"),
                PARSE_OPT_OPTARG),

        /* Options passed to git-fetch */
        OPT_GROUP(N_("Options related to fetching")),
        OPT_PASSTHRU(0, "all", &opt_all, NULL,
                N_("fetch from all remotes"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU('a', "append", &opt_append, NULL,
                N_("append to .git/FETCH_HEAD instead of overwriting"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "upload-pack", &opt_upload_pack, N_("path"),
                N_("path to upload pack on remote end"),
                0),
        OPT__FORCE(&opt_force, N_("force overwrite of local branch")),
        OPT_PASSTHRU('t', "tags", &opt_tags, NULL,
                N_("fetch all tags and associated objects"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU('p', "prune", &opt_prune, NULL,
                N_("prune remote-tracking branches no longer on remote"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "recurse-submodules", &opt_recurse_submodules,
                N_("on-demand"),
                N_("control recursive fetching of submodules"),
                PARSE_OPT_OPTARG),
        OPT_BOOL(0, "dry-run", &opt_dry_run,
                N_("dry run")),
        OPT_PASSTHRU('k', "keep", &opt_keep, NULL,
                N_("keep downloaded pack"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "depth", &opt_depth, N_("depth"),
                N_("deepen history of shallow clone"),
                0),
        OPT_PASSTHRU(0, "unshallow", &opt_unshallow, NULL,
                N_("convert to a complete repository"),
                PARSE_OPT_NONEG | PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "update-shallow", &opt_update_shallow, NULL,
                N_("accept refs that update .git/shallow"),
                PARSE_OPT_NOARG),
        OPT_PASSTHRU(0, "refmap", &opt_refmap, N_("refmap"),
                N_("specify fetch refmap"),
                PARSE_OPT_NONEG),

        OPT_END()
};

/**
 * Pushes "-q" or "-v" switches into arr to match the opt_verbosity level.
 */
static void argv_push_verbosity(struct argv_array *arr)
{
        int verbosity;

        for (verbosity = opt_verbosity; verbosity > 0; verbosity--)
                argv_array_push(arr, "-v");

        for (verbosity = opt_verbosity; verbosity < 0; verbosity++)
                argv_array_push(arr, "-q");
}

/**
 * Pushes "-f" switches into arr to match the opt_force level.
 */
static void argv_push_force(struct argv_array *arr)
{
        int force = opt_force;
        while (force-- > 0)
                argv_array_push(arr, "-f");
}

/**
 * Appends merge candidates from FETCH_HEAD that are not marked not-for-merge
 * into merge_heads.
 */
static void get_merge_heads(struct sha1_array *merge_heads)
{
        const char *filename = git_path("FETCH_HEAD");
        FILE *fp;
        struct strbuf sb = STRBUF_INIT;
        unsigned char sha1[GIT_SHA1_RAWSZ];

        if (!(fp = fopen(filename, "r")))
                die_errno(_("could not open '%s' for reading"), filename);
        while (strbuf_getline(&sb, fp, '\n') != EOF) {
                if (get_sha1_hex(sb.buf, sha1))
                        continue;  /* invalid line: does not start with SHA1 */
                if (starts_with(sb.buf + GIT_SHA1_HEXSZ, "\tnot-for-merge\t"))
                        continue;  /* ref is not-for-merge */
                sha1_array_append(merge_heads, sha1);
        }
        fclose(fp);
        strbuf_release(&sb);
}

/**
 * Used by die_no_merge_candidates() as a for_each_remote() callback to
 * retrieve the name of the remote if the repository only has one remote.
 */
static int get_only_remote(struct remote *remote, void *cb_data)
{
        const char **remote_name = cb_data;

        if (*remote_name)
                return -1;

        *remote_name = remote->name;
        return 0;
}

/**
 * Dies with the appropriate reason for why there are no merge candidates:
 *
 * 1. We fetched from a specific remote, and a refspec was given, but it ended
 *    up not fetching anything. This is usually because the user provided a
 *    wildcard refspec which had no matches on the remote end.
 *
 * 2. We fetched from a non-default remote, but didn't specify a branch to
 *    merge. We can't use the configured one because it applies to the default
 *    remote, thus the user must specify the branches to merge.
 *
 * 3. We fetched from the branch's or repo's default remote, but:
 *
 *    a. We are not on a branch, so there will never be a configured branch to
 *       merge with.
 *
 *    b. We are on a branch, but there is no configured branch to merge with.
 *
 * 4. We fetched from the branch's or repo's default remote, but the configured
 *    branch to merge didn't get fetched. (Either it doesn't exist, or wasn't
 *    part of the configured fetch refspec.)
 */
static void NORETURN die_no_merge_candidates(const char *repo, const char **refspecs)
{
        struct branch *curr_branch = branch_get("HEAD");
        const char *remote = curr_branch ? curr_branch->remote_name : NULL;

        if (*refspecs) {
                fprintf_ln(stderr, _("There are no candidates for merging among the refs that you just fetched."));
                fprintf_ln(stderr, _("Generally this means that you provided a wildcard refspec which had no\n"
                                        "matches on the remote end."));
        } else if (repo && curr_branch && (!remote || strcmp(repo, remote))) {
                fprintf_ln(stderr, _("You asked to pull from the remote '%s', but did not specify\n"
                        "a branch. Because this is not the default configured remote\n"
                        "for your current branch, you must specify a branch on the command line."),
                        repo);
        } else if (!curr_branch) {
                fprintf_ln(stderr, _("You are not currently on a branch."));
                fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
                fprintf_ln(stderr, _("See git-pull(1) for details."));
                fprintf(stderr, "\n");
                fprintf_ln(stderr, "    git pull <remote> <branch>");
                fprintf(stderr, "\n");
        } else if (!curr_branch->merge_nr) {
                const char *remote_name = NULL;

                if (for_each_remote(get_only_remote, &remote_name) || !remote_name)
                        remote_name = "<remote>";

                fprintf_ln(stderr, _("There is no tracking information for the current branch."));
                fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
                fprintf_ln(stderr, _("See git-pull(1) for details."));
                fprintf(stderr, "\n");
                fprintf_ln(stderr, "    git pull <remote> <branch>");
                fprintf(stderr, "\n");
                fprintf_ln(stderr, _("If you wish to set tracking information for this branch you can do so with:\n"
                                "\n"
                                "    git branch --set-upstream-to=%s/<branch> %s\n"),
                                remote_name, curr_branch->name);
        } else
                fprintf_ln(stderr, _("Your configuration specifies to merge with the ref '%s'\n"
                        "from the remote, but no such ref was fetched."),
                        *curr_branch->merge_name);
        exit(1);
}

/**
 * Parses argv into [<repo> [<refspecs>...]], returning their values in `repo`
 * as a string and `refspecs` as a null-terminated array of strings. If `repo`
 * is not provided in argv, it is set to NULL.
 */
static void parse_repo_refspecs(int argc, const char **argv, const char **repo,
                const char ***refspecs)
{
        if (argc > 0) {
                *repo = *argv++;
                argc--;
        } else
                *repo = NULL;
        *refspecs = argv;
}

/**
 * Runs git-fetch, returning its exit status. `repo` and `refspecs` are the
 * repository and refspecs to fetch, or NULL if they are not provided.
 */
static int run_fetch(const char *repo, const char **refspecs)
{
        struct argv_array args = ARGV_ARRAY_INIT;
        int ret;

        argv_array_pushl(&args, "fetch", "--update-head-ok", NULL);

        /* Shared options */
        argv_push_verbosity(&args);
        if (opt_progress)
                argv_array_push(&args, opt_progress);

        /* Options passed to git-fetch */
        if (opt_all)
                argv_array_push(&args, opt_all);
        if (opt_append)
                argv_array_push(&args, opt_append);
        if (opt_upload_pack)
                argv_array_push(&args, opt_upload_pack);
        argv_push_force(&args);
        if (opt_tags)
                argv_array_push(&args, opt_tags);
        if (opt_prune)
                argv_array_push(&args, opt_prune);
        if (opt_recurse_submodules)
                argv_array_push(&args, opt_recurse_submodules);
        if (opt_dry_run)
                argv_array_push(&args, "--dry-run");
        if (opt_keep)
                argv_array_push(&args, opt_keep);
        if (opt_depth)
                argv_array_push(&args, opt_depth);
        if (opt_unshallow)
                argv_array_push(&args, opt_unshallow);
        if (opt_update_shallow)
                argv_array_push(&args, opt_update_shallow);
        if (opt_refmap)
                argv_array_push(&args, opt_refmap);

        if (repo) {
                argv_array_push(&args, repo);
                argv_array_pushv(&args, refspecs);
        } else if (*refspecs)
                die("BUG: refspecs without repo?");
        ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
        argv_array_clear(&args);
        return ret;
}

/**
 * Runs git-merge, returning its exit status.
 */
static int run_merge(void)
{
        int ret;
        struct argv_array args = ARGV_ARRAY_INIT;

        argv_array_pushl(&args, "merge", NULL);

        /* Shared options */
        argv_push_verbosity(&args);
        if (opt_progress)
                argv_array_push(&args, opt_progress);

        /* Options passed to git-merge */
        if (opt_diffstat)
                argv_array_push(&args, opt_diffstat);
        if (opt_log)
                argv_array_push(&args, opt_log);
        if (opt_squash)
                argv_array_push(&args, opt_squash);
        if (opt_commit)
                argv_array_push(&args, opt_commit);
        if (opt_edit)
                argv_array_push(&args, opt_edit);
        if (opt_ff)
                argv_array_push(&args, opt_ff);
        if (opt_verify_signatures)
                argv_array_push(&args, opt_verify_signatures);
        argv_array_pushv(&args, opt_strategies.argv);
        argv_array_pushv(&args, opt_strategy_opts.argv);
        if (opt_gpg_sign)
                argv_array_push(&args, opt_gpg_sign);

        argv_array_push(&args, "FETCH_HEAD");
        ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
        argv_array_clear(&args);
        return ret;
}

int cmd_pull(int argc, const char **argv, const char *prefix)
{
        const char *repo, **refspecs;
        struct sha1_array merge_heads = SHA1_ARRAY_INIT;

        if (!getenv("_GIT_USE_BUILTIN_PULL")) {
                const char *path = mkpath("%s/git-pull", git_exec_path());

                if (sane_execvp(path, (char **)argv) < 0)
                        die_errno("could not exec %s", path);
        }

        argc = parse_options(argc, argv, prefix, pull_options, pull_usage, 0);

        parse_repo_refspecs(argc, argv, &repo, &refspecs);

        if (run_fetch(repo, refspecs))
                return 1;

        if (opt_dry_run)
                return 0;

        get_merge_heads(&merge_heads);

        if (!merge_heads.nr)
                die_no_merge_candidates(repo, refspecs);

        return run_merge();
}