fast-export, fast-import: add support for signed-commits

fast-export has a --signed-tags= option that controls how to handle tag
signatures.  However, there is no equivalent for commit signatures; it
just silently strips the signature out of the commit (analogously to
--signed-tags=strip).

While signatures are generally problematic for fast-export/fast-import
(because hashes are likely to change), if they're going to support tag
signatures, there's no reason to not also support commit signatures.

So, implement a --signed-commits= option that mirrors the --signed-tags=
option.

On the fast-export side, try to be as much like signed-tags as possible,
in both implementation and in user-interface.  This will change the
default behavior to '--signed-commits=abort' from what is now
'--signed-commits=strip'.  In order to provide an escape hatch for users
of third-party tools that call fast-export and do not yet know of the
--signed-commits= option, add an environment variable
'FAST_EXPORT_SIGNED_COMMITS_NOABORT=1' that changes the default to
'--signed-commits=warn-strip'.

Signed-off-by: Luke Shumaker <lukeshu@datawire.io>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/builtin/fast-import.c b/builtin/fast-import.c
index d6a368a566..a5b33eb91e 100644
--- a/builtin/fast-import.c
+++ b/builtin/fast-import.c
@@ -2719,10 +2719,13 @@ static struct hash_list *parse_merge(unsigned int *count)
 
 static void parse_new_commit(const char *arg)
 {
+	static struct strbuf sig = STRBUF_INIT;
 	static struct strbuf msg = STRBUF_INIT;
+	struct string_list siglines = STRING_LIST_INIT_NODUP;
 	struct branch *b;
 	char *author = NULL;
 	char *committer = NULL;
+	char *sig_alg = NULL;
 	char *encoding = NULL;
 	struct hash_list *merge_list = NULL;
 	unsigned int merge_count;
@@ -2746,6 +2749,13 @@ static void parse_new_commit(const char *arg)
 	}
 	if (!committer)
 		die("Expected committer but didn't get one");
+	if (skip_prefix(command_buf.buf, "gpgsig ", &v)) {
+		sig_alg = xstrdup(v);
+		read_next_command();
+		parse_data(&sig, 0, NULL);
+		read_next_command();
+	} else
+		strbuf_setlen(&sig, 0);
 	if (skip_prefix(command_buf.buf, "encoding ", &v)) {
 		encoding = xstrdup(v);
 		read_next_command();
@@ -2819,10 +2829,23 @@ static void parse_new_commit(const char *arg)
 		strbuf_addf(&new_data,
 			"encoding %s\n",
 			encoding);
+	if (sig_alg) {
+		if (!strcmp(sig_alg, "sha1"))
+			strbuf_addstr(&new_data, "gpgsig ");
+		else if (!strcmp(sig_alg, "sha256"))
+			strbuf_addstr(&new_data, "gpgsig-sha256 ");
+		else
+			die("Expected gpgsig algorithm sha1 or sha256, got %s", sig_alg);
+		string_list_split_in_place(&siglines, sig.buf, "\n", -1);
+		strbuf_add_separated_string_list(&new_data, "\n ", &siglines);
+		strbuf_addch(&new_data, '\n');
+	}
 	strbuf_addch(&new_data, '\n');
 	strbuf_addbuf(&new_data, &msg);
+	string_list_clear(&siglines, 1);
 	free(author);
 	free(committer);
+	free(sig_alg);
 	free(encoding);
 
 	if (!store_object(OBJ_COMMIT, &new_data, NULL, &b->oid, next_mark))