archive: support compression levels beyond 9

Compression programs like zip, gzip, bzip2 and xz allow to adjust the
trade-off between CPU cost and size gain with numerical options from -1
for fast compression and -9 for high compression ratio.  zip also
accepts -0 for storing files verbatim.  git archive directly support
these single-digit compression levels for ZIP output and passes them to
filters like gzip.

Zstandard additionally supports compression level options -10 to -19, or
up to -22 with --ultra.  This *seems* to work with git archive in most
cases, e.g. it will produce an archive with -19 without complaining, but
since it only supports single-digit compression level options this is
the same as -1 -9 and thus -9.

Allow git archive to accept multi-digit compression levels to support
the full range supported by zstd.  Explicitly reject them for the ZIP
format, as otherwise deflateInit2() would just fail with a somewhat
cryptic "stream consistency error".

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

archive-tar.c

@@ -374,7 +374,8 @@ static int tar_filter_config(const char *var, const char *value, void *data)
 		ar = xcalloc(1, sizeof(*ar));
 		ar->name = xmemdupz(name, namelen);
 		ar->write_archive = write_tar_filter_archive;
-		ar->flags = ARCHIVER_WANT_COMPRESSION_LEVELS;
+		ar->flags = ARCHIVER_WANT_COMPRESSION_LEVELS |
+			    ARCHIVER_HIGH_COMPRESSION_LEVELS;
 		ALLOC_GROW(tar_filters, nr_tar_filters + 1, alloc_tar_filters);
 		tar_filters[nr_tar_filters++] = ar;
 	}

archive.c

@@ -529,10 +529,12 @@ static int add_file_cb(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
-#define OPT__COMPR(s, v, h, p) \
-	OPT_SET_INT_F(s, NULL, v, h, p, PARSE_OPT_NONEG)
-#define OPT__COMPR_HIDDEN(s, v, p) \
-	OPT_SET_INT_F(s, NULL, v, "", p, PARSE_OPT_NONEG | PARSE_OPT_HIDDEN)
+static int number_callback(const struct option *opt, const char *arg, int unset)
+{
+	BUG_ON_OPT_NEG(unset);
+	*(int *)opt->value = strtol(arg, NULL, 10);
+	return 0;
+}
 
 static int parse_archive_args(int argc, const char **argv,
 		const struct archiver **ar, struct archiver_args *args,
@@ -561,16 +563,8 @@ static int parse_archive_args(int argc, const char **argv,
 		OPT_BOOL(0, "worktree-attributes", &worktree_attributes,
 			N_("read .gitattributes in working directory")),
 		OPT__VERBOSE(&verbose, N_("report archived files on stderr")),
-		OPT__COMPR('0', &compression_level, N_("store only"), 0),
-		OPT__COMPR('1', &compression_level, N_("compress faster"), 1),
-		OPT__COMPR_HIDDEN('2', &compression_level, 2),
-		OPT__COMPR_HIDDEN('3', &compression_level, 3),
-		OPT__COMPR_HIDDEN('4', &compression_level, 4),
-		OPT__COMPR_HIDDEN('5', &compression_level, 5),
-		OPT__COMPR_HIDDEN('6', &compression_level, 6),
-		OPT__COMPR_HIDDEN('7', &compression_level, 7),
-		OPT__COMPR_HIDDEN('8', &compression_level, 8),
-		OPT__COMPR('9', &compression_level, N_("compress better"), 9),
+		OPT_NUMBER_CALLBACK(&compression_level,
+			N_("set compression level"), number_callback),
 		OPT_GROUP(""),
 		OPT_BOOL('l', "list", &list,
 			N_("list supported archive formats")),
@@ -617,7 +611,9 @@ static int parse_archive_args(int argc, const char **argv,
 
 	args->compression_level = Z_DEFAULT_COMPRESSION;
 	if (compression_level != -1) {
-		if ((*ar)->flags & ARCHIVER_WANT_COMPRESSION_LEVELS)
+		int levels_ok = (*ar)->flags & ARCHIVER_WANT_COMPRESSION_LEVELS;
+		int high_ok = (*ar)->flags & ARCHIVER_HIGH_COMPRESSION_LEVELS;
+		if (levels_ok && (compression_level <= 9 || high_ok))
 			args->compression_level = compression_level;
 		else {
 			die(_("Argument not supported for format '%s': -%d"),

archive.h

@@ -36,6 +36,7 @@ const char *archive_format_from_filename(const char *filename);
 
 #define ARCHIVER_WANT_COMPRESSION_LEVELS 1
 #define ARCHIVER_REMOTE 2
+#define ARCHIVER_HIGH_COMPRESSION_LEVELS 4
 struct archiver {
 	const char *name;
 	int (*write_archive)(const struct archiver *, struct archiver_args *);