Subject: Re: [PATCH 1/2] repack: rewrite the shell script in C

From: René Scharfe <[email-masked]>
Date: Sun, 15 Sep 2013 13:42:08 +0200

Am 29.08.2013 22:39, schrieb Stefan Beller:
> The motivation of this patch is to get closer to a goal of being
> able to have a core subset of git functionality built in to git.
> That would mean
>
>  * people on Windows could get a copy of at least the core parts
>    of Git without having to install a Unix-style shell
>
>  * people using git in on servers with chrooted environments
>    do not need to worry about standard tools lacking for shell
>    scripts.
>
> This patch is meant to be mostly a literal translation of the
> git-repack script; the intent is that later patches would start using
> more library facilities, but this patch is meant to be as close to a
> no-op as possible so it doesn't do that kind of thing.
>
> Signed-off-by: Stefan Beller <[email-masked]>
> ---
>  Makefile                                        |   2 +-
>  builtin.h                                       |   1 +
>  builtin/repack.c                                | 379 ++++++++++++++++++++++++
>  git-repack.sh => contrib/examples/git-repack.sh |   0
>  git.c                                           |   1 +
>  5 files changed, 382 insertions(+), 1 deletion(-)
>  create mode 100644 builtin/repack.c
>  rename git-repack.sh => contrib/examples/git-repack.sh (100%)
>
> diff --git a/Makefile b/Makefile
> index 3588ca1..69e5267 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -464,7 +464,6 @@ SCRIPT_SH += git-pull.sh
>  SCRIPT_SH += git-quiltimport.sh
>  SCRIPT_SH += git-rebase.sh
>  SCRIPT_SH += git-remote-testgit.sh
> -SCRIPT_SH += git-repack.sh
>  SCRIPT_SH += git-request-pull.sh
>  SCRIPT_SH += git-stash.sh
>  SCRIPT_SH += git-submodule.sh
> @@ -971,6 +970,7 @@ BUILTIN_OBJS += builtin/reflog.o
>  BUILTIN_OBJS += builtin/remote.o
>  BUILTIN_OBJS += builtin/remote-ext.o
>  BUILTIN_OBJS += builtin/remote-fd.o
> +BUILTIN_OBJS += builtin/repack.o
>  BUILTIN_OBJS += builtin/replace.o
>  BUILTIN_OBJS += builtin/rerere.o
>  BUILTIN_OBJS += builtin/reset.o
> diff --git a/builtin.h b/builtin.h
> index 8afa2de..b56cf07 100644
> --- a/builtin.h
> +++ b/builtin.h
> @@ -102,6 +102,7 @@ extern int cmd_reflog(int argc, const char **argv, const char *prefix);
>  extern int cmd_remote(int argc, const char **argv, const char *prefix);
>  extern int cmd_remote_ext(int argc, const char **argv, const char *prefix);
>  extern int cmd_remote_fd(int argc, const char **argv, const char *prefix);
> +extern int cmd_repack(int argc, const char **argv, const char *prefix);
>  extern int cmd_repo_config(int argc, const char **argv, const char *prefix);
>  extern int cmd_rerere(int argc, const char **argv, const char *prefix);
>  extern int cmd_reset(int argc, const char **argv, const char *prefix);
> diff --git a/builtin/repack.c b/builtin/repack.c
> new file mode 100644
> index 0000000..0cc823d
> --- /dev/null
> +++ b/builtin/repack.c
> @@ -0,0 +1,379 @@
> +#include "builtin.h"
> +#include "cache.h"
> +#include "dir.h"
> +#include "parse-options.h"
> +#include "run-command.h"
> +#include "sigchain.h"
> +#include "strbuf.h"
> +#include "string-list.h"
> +#include "argv-array.h"
> +
> +static int delta_base_offset = 1;
> +static char *packdir, *packtmp;
> +
> +static const char *const git_repack_usage[] = {
> +	N_("git repack [options]"),
> +	NULL
> +};
> +
> +static int repack_config(const char *var, const char *value, void *cb)
> +{
> +	if (!strcmp(var, "repack.usedeltabaseoffset")) {
> +		delta_base_offset = git_config_bool(var, value);
> +		return 0;
> +	}
> +	return git_default_config(var, value, cb);
> +}
> +
> +/*
> + * Remove temporary $GIT_OBJECT_DIRECTORY/pack/.tmp-$$-pack-* files.
> + */
> +static void remove_temporary_files(void)
> +{
> +	struct strbuf buf = STRBUF_INIT;
> +	size_t dirlen, prefixlen;
> +	DIR *dir;
> +	struct dirent *e;
> +
> +	dir = opendir(packdir);
> +	if (!dir)
> +		return;
> +
> +	strbuf_addstr(&buf, packdir);

Let's say packdir is ".git/objects/pack" (no trailing slash).  Then buf 
is ".git/objects/pack" now as well.

> +
> +	/* Point at the slash at the end of ".../objects/pack/" */
> +	dirlen = buf.len + 1;
> +	strbuf_addf(&buf, "%s", packtmp);

packtmp starts with packdir, so by adding it here we have it twice.  buf 
is now ".git/objects/pack.git/objects/pack/.tmp-123-pack" (if our pid is 
123), no?

Perhaps don't add the packdir to the strbuf in the first place and 
calculate dirlen as strlen(packdir) + 1?

Besided, strbuf_addstr(x, y) is better for adding a string than 
strbuf_addf(x, "%s", y).

> +	/* Point at the dash at the end of ".../.tmp-%d-pack-" */
> +	prefixlen = buf.len - dirlen;

This is the length of "git/objects/pack/.tmp-123-pack" now.

> +
> +	while ((e = readdir(dir))) {
> +		if (strncmp(e->d_name, buf.buf + dirlen, prefixlen))
> +			continue;
> +		strbuf_setlen(&buf, dirlen);
> +		strbuf_addstr(&buf, e->d_name);
> +		unlink(buf.buf);
> +	}
> +	closedir(dir);
> +	strbuf_release(&buf);
> +}
> +
> +static void remove_pack_on_signal(int signo)
> +{
> +	remove_temporary_files();
> +	sigchain_pop(signo);
> +	raise(signo);
> +}
> +
> +/*
> + * Adds all packs hex strings to the fname list, which do not
> + * have a corresponding .keep file.
> + */
> +static void get_non_kept_pack_filenames(struct string_list *fname_list)
> +{
> +	DIR *dir;
> +	struct dirent *e;
> +	char *fname;
> +	size_t len;
> +
> +	if (!(dir = opendir(packdir)))
> +		return;
> +
> +	while ((e = readdir(dir)) != NULL) {
> +		if (suffixcmp(e->d_name, ".pack"))
> +			continue;
> +
> +		len = strlen(e->d_name) - strlen(".pack");
> +		fname = xmemdupz(e->d_name, len);
> +
> +		if (!file_exists(mkpath("%s/%s.keep", packdir, fname)))
> +			string_list_append_nodup(fname_list, fname);

This leaks fname for packs with .keep files.

> +	}
> +	closedir(dir);
> +}
> +
> +static void remove_redundant_pack(const char *path_prefix, const char *hex)
> +{
> +	const char *exts[] = {".pack", ".idx", ".keep"};
> +	int i;
> +	struct strbuf buf = STRBUF_INIT;
> +	size_t plen;
> +
> +	strbuf_addf(&buf, "%s/%s", path_prefix, hex);
> +	plen = buf.len;
> +
> +	for (i = 0; i < ARRAY_SIZE(exts); i++) {
> +		strbuf_setlen(&buf, plen);
> +		strbuf_addstr(&buf, exts[i]);
> +		unlink(buf.buf);
> +	}
> +}

hex must also include the "pack-" prefix and path_prefix must be a 
directory name.  Perhaps call them base_name and dir_name or similar to 
make that clearer?

buf is leaked.

> +
> +#define ALL_INTO_ONE 1
> +#define LOOSE_UNREACHABLE 2
> +
> +int cmd_repack(int argc, const char **argv, const char *prefix)
> +{
> +	const char *exts[2] = {".pack", ".idx"};
> +	struct child_process cmd;
> +	struct string_list_item *item;
> +	struct argv_array cmd_args = ARGV_ARRAY_INIT;
> +	struct string_list names = STRING_LIST_INIT_DUP;
> +	struct string_list rollback = STRING_LIST_INIT_NODUP;
> +	struct string_list existing_packs = STRING_LIST_INIT_DUP;
> +	struct strbuf line = STRBUF_INIT;
> +	int nr_packs, ext, ret, failed;
> +	FILE *out;
> +
> +	/* variables to be filled by option parsing */
> +	int pack_everything = 0;
> +	int delete_redundant = 0;
> +	char *unpack_unreachable = NULL;
> +	int window = 0, window_memory = 0;
> +	int depth = 0;
> +	int max_pack_size = 0;
> +	int no_reuse_delta = 0, no_reuse_object = 0;
> +	int no_update_server_info = 0;
> +	int quiet = 0;
> +	int local = 0;
> +
> +	struct option builtin_repack_options[] = {
> +		OPT_BIT('a', NULL, &pack_everything,
> +				N_("pack everything in a single pack"), ALL_INTO_ONE),
> +		OPT_BIT('A', NULL, &pack_everything,
> +				N_("same as -a, and turn unreachable objects loose"), LOOSE_UNREACHABLE),
> +		OPT_BOOL('d', NULL, &delete_redundant,
> +				N_("remove redundant packs, and run git-prune-packed")),
> +		OPT_BOOL('f', NULL, &no_reuse_delta,
> +				N_("pass --no-reuse-delta to git-pack-objects")),
> +		OPT_BOOL('F', NULL, &no_reuse_object,
> +				N_("pass --no-reuse-object to git-pack-objects")),
> +		OPT_BOOL('n', NULL, &no_update_server_info,
> +				N_("do not run git-update-server-info")),
> +		OPT__QUIET(&quiet, N_("be quiet")),
> +		OPT_BOOL('l', "local", &local,
> +				N_("pass --local to git-pack-objects")),
> +		OPT_STRING(0, "unpack-unreachable", &unpack_unreachable, N_("approxidate"),
> +				N_("with -A, do not loosen objects older than this")),
> +		OPT_INTEGER(0, "window", &window,
> +				N_("size of the window used for delta compression")),
> +		OPT_INTEGER(0, "window-memory", &window_memory,
> +				N_("same as the above, but limit memory size instead of entries count")),
> +		OPT_INTEGER(0, "depth", &depth,
> +				N_("limits the maximum delta depth")),
> +		OPT_INTEGER(0, "max-pack-size", &max_pack_size,
> +				N_("maximum size of each packfile")),
> +		OPT_END()
> +	};
> +
> +	git_config(repack_config, NULL);
> +
> +	argc = parse_options(argc, argv, prefix, builtin_repack_options,
> +				git_repack_usage, 0);
> +
> +	packdir = mkpathdup("%s/pack", get_object_directory());
> +	packtmp = mkpathdup("%s/.tmp-%d-pack", packdir, (int)getpid());
> +
> +	sigchain_push_common(remove_pack_on_signal);
> +
> +	argv_array_push(&cmd_args, "pack-objects");
> +	argv_array_push(&cmd_args, "--keep-true-parents");
> +	argv_array_push(&cmd_args, "--honor-pack-keep");
> +	argv_array_push(&cmd_args, "--non-empty");
> +	argv_array_push(&cmd_args, "--all");
> +	argv_array_push(&cmd_args, "--reflog");
> +	if (window)
> +		argv_array_pushf(&cmd_args, "--window=%u", window);
> +	if (window_memory)
> +		argv_array_pushf(&cmd_args, "--window-memory=%u", window_memory);
> +	if (depth)
> +		argv_array_pushf(&cmd_args, "--depth=%u", depth);
> +	if (max_pack_size)
> +		argv_array_pushf(&cmd_args, "--max_pack_size=%u", max_pack_size);
> +	if (no_reuse_delta)
> +		argv_array_pushf(&cmd_args, "--no-reuse-delta");
> +	if (no_reuse_object)
> +		argv_array_pushf(&cmd_args, "--no-reuse-object");
> +
> +	if (!pack_everything) {
> +		argv_array_push(&cmd_args, "--unpacked");
> +		argv_array_push(&cmd_args, "--incremental");
> +	} else {
> +		get_non_kept_pack_filenames(&existing_packs);
> +
> +		if (existing_packs.nr && delete_redundant) {
> +			if (unpack_unreachable)
> +				argv_array_pushf(&cmd_args,
> +						"--unpack-unreachable=%s",
> +						unpack_unreachable);
> +			else if (pack_everything & LOOSE_UNREACHABLE)
> +				argv_array_push(&cmd_args,
> +						"--unpack-unreachable");
> +		}
> +	}
> +
> +	if (local)
> +		argv_array_push(&cmd_args,  "--local");
> +	if (quiet)
> +		argv_array_push(&cmd_args,  "--quiet");
> +	if (delta_base_offset)
> +		argv_array_push(&cmd_args,  "--delta-base-offset");
> +
> +	argv_array_push(&cmd_args, packtmp);
> +
> +	memset(&cmd, 0, sizeof(cmd));
> +	cmd.argv = cmd_args.argv;
> +	cmd.git_cmd = 1;
> +	cmd.out = -1;
> +	cmd.no_stdin = 1;
> +
> +	ret = start_command(&cmd);
> +	if (ret)
> +		return 1;
> +
> +	nr_packs = 0;
> +	out = xfdopen(cmd.out, "r");
> +	while (strbuf_getline(&line, out, '\n') != EOF) {
> +		if (line.len != 40)
> +			die("repack: Expecting 40 character sha1 lines only from pack-objects.");
> +		string_list_append(&names, line.buf);
> +		nr_packs++;
> +	}
> +	fclose(out);
> +	ret = finish_command(&cmd);
> +	if (ret)
> +		return 1;
> +	argv_array_clear(&cmd_args);
> +
> +	if (!nr_packs && !quiet)
> +		printf("Nothing new to pack.\n");
> +
> +	/*
> +	 * Ok we have prepared all new packfiles.
> +	 * First see if there are packs of the same name and if so
> +	 * if we can move them out of the way (this can happen if we
> +	 * repacked immediately after packing fully.
> +	 */
> +	failed = 0;
> +	for_each_string_list_item(item, &names) {
> +		for (ext = 0; ext < 2; ext++) {
> +			char *fname, *fname_old;
> +			fname = mkpathdup("%s/%s%s", packdir,
> +						item->string, exts[ext]);
> +			if (!file_exists(fname)) {
> +				free(fname);
> +				continue;
> +			}
> +
> +			fname_old = mkpath("%s/old-%s%s", packdir,
> +						item->string, exts[ext]);
> +			if (file_exists(fname_old))
> +				if (unlink(fname_old))
> +					failed = 1;
> +
> +			if (!failed && rename(fname, fname_old)) {
> +				failed = 1;
> +				break;

This leaks fname.

> +			}
> +			string_list_append(&rollback, fname);

Mental note: This is effectively string_list_append_nodup because 
rollback is initialized with STRING_LIST_INIT_NODUP, so there's no leak 
here.

> +		}
> +		if (failed)
> +			break;
> +	}
> +	if (failed) {
> +		struct string_list rollback_failure = STRING_LIST_INIT_DUP;
> +		for_each_string_list_item(item, &rollback) {
> +			char *fname, *fname_old;
> +			fname = mkpathdup("%s/%s", packdir, item->string);
> +			fname_old = mkpath("%s/old-%s", packdir, item->string);
> +			if (rename(fname_old, fname))
> +				string_list_append(&rollback_failure, fname);
> +			free(fname);
> +		}
> +
> +		if (rollback_failure.nr) {
> +			int i;
> +			fprintf(stderr,
> +				"WARNING: Some packs in use have been renamed by\n"
> +				"WARNING: prefixing old- to their name, in order to\n"
> +				"WARNING: replace them with the new version of the\n"
> +				"WARNING: file.  But the operation failed, and the\n"
> +				"WARNING: attempt to rename them back to their\n"
> +				"WARNING: original names also failed.\n"
> +				"WARNING: Please rename them in %s manually:\n", packdir);
> +			for (i = 0; i < rollback_failure.nr; i++)
> +				fprintf(stderr, "WARNING:   old-%s -> %s\n",
> +					rollback_failure.items[i].string,
> +					rollback_failure.items[i].string);
> +		}
> +		exit(1);
> +	}
> +
> +	/* Now the ones with the same name are out of the way... */
> +	for_each_string_list_item(item, &names) {
> +		for (ext = 0; ext < 2; ext++) {
> +			char *fname, *fname_old;
> +			struct stat statbuffer;
> +			fname = mkpathdup("%s/pack-%s%s",
> +					packdir, item->string, exts[ext]);
> +			fname_old = mkpathdup("%s-%s%s",
> +					packtmp, item->string, exts[ext]);
> +			if (!stat(fname_old, &statbuffer)) {
> +				statbuffer.st_mode &= ~(S_IWUSR | S_IWGRP | S_IWOTH);
> +				chmod(fname_old, statbuffer.st_mode);
> +			}
> +			if (rename(fname_old, fname))
> +				die_errno(_("renaming '%s' failed"), fname_old);

The Shell script exits silently in that case.  How about improving error 
reporting in a separate patch?

> +			free(fname);
> +			free(fname_old);
> +		}
> +	}
> +
> +	/* Remove the "old-" files */
> +	for_each_string_list_item(item, &names) {
> +		for (ext = 0; ext < 2; ext++) {
> +			char *fname;
> +			fname = mkpath("%s/old-pack-%s%s",
> +					packdir,
> +					item->string,
> +					exts[ext]);
> +			if (remove_path(fname))
> +				warning(_("removing '%s' failed"), fname);

Similar case here: The Shell script continues silently.

> +		}
> +	}
> +
> +	/* End of pack replacement. */
> +
> +	if (delete_redundant) {
> +		sort_string_list(&names);
> +		for_each_string_list_item(item, &existing_packs) {
> +			char *sha1;
> +			size_t len = strlen(item->string);
> +			if (len < 40)
> +				continue;
> +			sha1 = item->string + len - 40;
> +			if (!string_list_has_string(&names, sha1))
> +				remove_redundant_pack(packdir, item->string);
> +		}
> +		argv_array_push(&cmd_args, "prune-packed");
> +		if (quiet)
> +			argv_array_push(&cmd_args, "--quiet");
> +
> +		memset(&cmd, 0, sizeof(cmd));
> +		cmd.argv = cmd_args.argv;
> +		cmd.git_cmd = 1;
> +		run_command(&cmd);
> +		argv_array_clear(&cmd_args);
> +	}
> +
> +	if (!no_update_server_info) {
> +		argv_array_push(&cmd_args, "update-server-info");
> +		memset(&cmd, 0, sizeof(cmd));
> +		cmd.argv = cmd_args.argv;
> +		cmd.git_cmd = 1;
> +		run_command(&cmd);
> +		argv_array_clear(&cmd_args);
> +	}
> +	remove_temporary_files();

If you take care to clear the argv_arrays then perhaps do the same for 
the string_lists?  The OS cleans up after us anyway, but calming 
Valgrind or similar leak checkers is a good practice nevertheless.

> +	return 0;
> +}
> diff --git a/git-repack.sh b/contrib/examples/git-repack.sh
> similarity index 100%
> rename from git-repack.sh
> rename to contrib/examples/git-repack.sh
> diff --git a/git.c b/git.c
> index 2025f77..03510be 100644
> --- a/git.c
> +++ b/git.c
> @@ -396,6 +396,7 @@ static void handle_internal_command(int argc, const char **argv)
>  		{ "remote", cmd_remote, RUN_SETUP },
>  		{ "remote-ext", cmd_remote_ext },
>  		{ "remote-fd", cmd_remote_fd },
> +		{ "repack", cmd_repack, RUN_SETUP },
>  		{ "replace", cmd_replace, RUN_SETUP },
>  		{ "repo-config", cmd_repo_config, RUN_SETUP_GENTLY },
>  		{ "rerere", cmd_rerere, RUN_SETUP },
> -- 1.8.4
>