Subject: Re: [PATCH] fast-(import|export): improve on the signature algorithm name

From: Junio C Hamano <[email-masked]>
Date: Wed, 28 May 2025 10:29:19 -0700

Junio C Hamano <[email-masked]> writes:

> Christian Couder <[email-masked]> writes:
>
>> I agree that we should have at least said in big letters that the
>> improved support for signed commits in fast-export/import is very
>> experimental and very likely to change in the future.
>>
>> We could still do so. This could give us a bit of time and flexibility
>> until we agree on and implement something better and backward
>> compatible. (Hopefully the v2 will help us move forward.)
>
> OK, as the next release is approaching, perhaps we do a bit of
> documentation update to address that "we are experimenting" and
> nothing else, and leave the v2 updates for the next cycle?

---- >8 ----
Subject: [PATCH] fast-export: --signed-commits is experimental

As the design of signature handling is still being discussed, it is
likely that the data stream produced by the code in Git 2.50 would
have to be changed in such a way that is not backward compatible.

Mark the feature as experimental and discourge its use for now.

Also flip the default on the generation side to "strip"; users of
existing versions would not have passed --signed-commits=strip and
will be broken by this change if the default is made to abort, and
will be encouraged by the error message to produce data stream with
future breakage guarantees by passing --signed-commits option.

As we tone down the default behaviour, we no longer need the
FAST_EXPORT_SIGNED_COMMITS_NOABORT environment variable, which was
not discoverable enough.

Signed-off-by: Junio C Hamano <[email-masked]>
---
 Documentation/RelNotes/2.50.0.adoc |  4 +++-
 Documentation/git-fast-export.adoc | 12 +++++-------
 Documentation/git-fast-import.adoc |  3 +++
 builtin/fast-export.c              |  7 +------
 t/t9350-fast-export.sh             | 20 ++++----------------
 5 files changed, 16 insertions(+), 30 deletions(-)

diff --git a/Documentation/RelNotes/2.50.0.adoc b/Documentation/RelNotes/2.50.0.adoc
index c6c34d1a1d..9a1cdf0dc0 100644
--- a/Documentation/RelNotes/2.50.0.adoc
+++ b/Documentation/RelNotes/2.50.0.adoc
@@ -100,7 +100,9 @@ Performance, Internal Implementation, Development Support etc.
  * "git fsck" becomes more careful when checking the refs.
 
  * "git fast-export | git fast-import" learns to deal with commit and
-   tag objects with embedded signatures a bit better.
+   tag objects with embedded signatures a bit better.  This is highly
+   experimental and the format of the data stream may change in the
+   future without compatibility guarantees.
 
  * The code paths to check whether a refname X is available (by seeing
    if another ref X/Y exists, etc.) have been optimized.
diff --git a/Documentation/git-fast-export.adoc b/Documentation/git-fast-export.adoc
index 413a527496..43bbb4f63c 100644
--- a/Documentation/git-fast-export.adoc
+++ b/Documentation/git-fast-export.adoc
@@ -46,14 +46,12 @@ resulting tag will have an invalid signature.
 
 --signed-commits=(verbatim|warn-verbatim|warn-strip|strip|abort)::
 	Specify how to handle signed commits.  Behaves exactly as
-	'--signed-tags', but for commits.  Default is 'abort'.
+	'--signed-tags', but for commits.  Default is 'strip', which
+	is the same as how earlier versions of this command without
+	this option behaved.
 +
-Earlier versions this command that did not have '--signed-commits'
-behaved as if '--signed-commits=strip'.  As an escape hatch for users
-of tools that call 'git fast-export' but do not yet support
-'--signed-commits', you may set the environment variable
-'FAST_EXPORT_SIGNED_COMMITS_NOABORT=1' in order to change the default
-from 'abort' to 'warn-strip'.
+NOTE: This is highly experimental and the format of the data stream may
+change in the future without compatibility guarantees.
 
 --tag-of-filtered-object=(abort|drop|rewrite)::
 	Specify how to handle tags whose tagged object is filtered out.
diff --git a/Documentation/git-fast-import.adoc b/Documentation/git-fast-import.adoc
index 7b107f5e8e..250d866652 100644
--- a/Documentation/git-fast-import.adoc
+++ b/Documentation/git-fast-import.adoc
@@ -523,6 +523,9 @@ that signs the commit data.
 Here <alg> specifies which hashing algorithm is used for this
 signature, either `sha1` or `sha256`.
 
+NOTE: This is highly experimental and the format of the data stream may
+change in the future without compatibility guarantees.
+
 `encoding`
 ^^^^^^^^^^
 The optional `encoding` command indicates the encoding of the commit
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 37c01d6c6f..fcf6b00d5f 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -39,7 +39,7 @@ enum sign_mode { SIGN_ABORT, SIGN_VERBATIM, SIGN_STRIP, SIGN_WARN_VERBATIM, SIGN
 
 static int progress;
 static enum sign_mode signed_tag_mode = SIGN_ABORT;
-static enum sign_mode signed_commit_mode = SIGN_ABORT;
+static enum sign_mode signed_commit_mode = SIGN_STRIP;
 static enum tag_of_filtered_mode { TAG_FILTERING_ABORT, DROP, REWRITE } tag_of_filtered_mode = TAG_FILTERING_ABORT;
 static enum reencode_mode { REENCODE_ABORT, REENCODE_YES, REENCODE_NO } reencode_mode = REENCODE_ABORT;
 static int fake_missing_tagger;
@@ -1269,7 +1269,6 @@ int cmd_fast_export(int argc,
 		    const char *prefix,
 		    struct repository *repo UNUSED)
 {
-	const char *env_signed_commits_noabort;
 	struct rev_info revs;
 	struct commit *commit;
 	char *export_filename = NULL,
@@ -1327,10 +1326,6 @@ int cmd_fast_export(int argc,
 	if (argc == 1)
 		usage_with_options (fast_export_usage, options);
 
-	env_signed_commits_noabort = getenv("FAST_EXPORT_SIGNED_COMMITS_NOABORT");
-	if (env_signed_commits_noabort && *env_signed_commits_noabort)
-		signed_commit_mode = SIGN_WARN_STRIP;
-
 	/* we handle encodings */
 	git_config(git_default_config, NULL);
 
diff --git a/t/t9350-fast-export.sh b/t/t9350-fast-export.sh
index dda9e7c3e7..76619765fc 100755
--- a/t/t9350-fast-export.sh
+++ b/t/t9350-fast-export.sh
@@ -299,22 +299,10 @@ test_expect_success GPG 'set up signed commit' '
 
 '
 
-test_expect_success GPG 'signed-commits default' '
-
-	sane_unset FAST_EXPORT_SIGNED_COMMITS_NOABORT &&
-	test_must_fail git fast-export --reencode=no commit-signing &&
-
-	FAST_EXPORT_SIGNED_COMMITS_NOABORT=1 git fast-export --reencode=no commit-signing >output 2>err &&
-	! grep ^gpgsig output &&
-	grep "^encoding ISO-8859-1" output &&
-	test -s err &&
-	sed "s/commit-signing/commit-strip-signing/" output | (
-		cd new &&
-		git fast-import &&
-		STRIPPED=$(git rev-parse --verify refs/heads/commit-strip-signing) &&
-		test $COMMIT_SIGNING != $STRIPPED
-	)
-
+test_expect_success GPG 'signed-commits default is same as strip' '
+	git fast-export --reencode=no commit-signing >out1 2>err &&
+	git fast-export --reencode=no --signed-commits=strip commit-signing >out2 &&
+	test_cmp out1 out2
 '
 
 test_expect_success GPG 'signed-commits=abort' '
-- 
2.50.0-rc0-134-gb29a910c2a