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Re: [PATCH v2 1/1] replay: make atomic ref updates the default behavior

From
PWPhillip Wood <phillip.wood123@gmail.com>
Date
Sep 30, 2025, 10:05 UTC
Message-ID
<9052eccc-1121-442f-ad51-4fe9217024a0@gmail.com>
In-Reply-To
<20250926230838.35870-2-siddharthasthana31@gmail.com>
Hi Siddharth
On 27/09/2025 00:08, Siddharth Asthana wrote:
Show 8 quoted lines
> The git replay command currently outputs update commands that must be
> piped to git update-ref --stdin to actually update references:
> 
>      git replay --onto main topic1..topic2 | git update-ref --stdin
> 
> This design has significant limitations for server-side operations. The
> two-command pipeline creates coordination complexity, provides no atomic
> transaction guarantees by default

Are you sure that's true? Maybe I'm missing something but my reading of builtin/update-ref.c is that it when "--stdin" is given it starts a ref transaction, reads the commands from stdin and applies them to that transaction and then commits the transaction which will make the updates atomic.

> , and complicates automation in bare
> repository environments where git replay is primarily used.
How does it complicate automation in bare repositories?

Christian has given detailed feedback on the rest of the commit message so I'll not comment on it further.

Show 10 quoted lines
> diff --git a/Documentation/git-replay.adoc b/Documentation/git-replay.adoc
> index 0b12bf8aa4..e104e0bc03 100644
> --- a/Documentation/git-replay.adoc
> +++ b/Documentation/git-replay.adoc
> @@ -9,16 +9,16 @@ git-replay - EXPERIMENTAL: Replay commits on a new base, works with bare repos t
>   SYNOPSIS
>   --------
>   [verse]
> -(EXPERIMENTAL!) 'git replay' ([--contained] --onto <newbase> | --advance <branch>) <revision-range>...
> +(EXPERIMENTAL!) 'git replay' ([--contained] --onto <newbase> | --advance <branch>) [--output-commands | --allow-partial] <revision-range>...
Please wrap this very long line
Show 17 quoted lines
> @@ -42,6 +42,20 @@ When `--advance` is specified, the update-ref command(s) in the output
>   will update the branch passed as an argument to `--advance` to point at
>   the new commits (in other words, this mimics a cherry-pick operation).
>   
> +--output-commands::
> +	Output update-ref commands instead of updating refs directly.
> +	When this option is used, the output can be piped to `git update-ref --stdin`
> +	for successive, relatively slow, ref updates. This is equivalent to the
> +	old default behavior.
> +
> +--allow-partial::
> +	Allow some ref updates to succeed even if others fail. By default,
> +	ref updates are atomic (all succeed or all fail). With this option,
> +	failed updates are reported as warnings rather than causing the entire
> +	command to fail. The command exits with code 0 only if all updates
> +	succeed; any failures result in exit code 1. Cannot be used with
> +	`--output-commands`.

Rather than having two incompatible options perhaps we could have a single "--update-refs=(yes|print|allow-partial-updates)" argument. I think the name "--allow-partial" is rather ambiguous as it does not say what it is allowing to be partial.

Show 9 quoted lines
> +static int add_ref_to_transaction(struct ref_transaction *transaction,
> +				  const char *refname,
> +				  const struct object_id *new_oid,
> +				  const struct object_id *old_oid,
> +				  struct strbuf *err)
> +{
> +	return ref_transaction_update(transaction, refname, new_oid, old_oid,
> +				      NULL, NULL, 0, "git replay", err);
> +}

I'm not sure this function adds much value. I think it would be better to instead have a helper function that updates refs or prints the ref updates so that we do not duplicate that code in the two places below.

Show 21 quoted lines
> @@ -434,10 +481,18 @@ int cmd_replay(int argc,
>   			if (decoration->type == DECORATION_REF_LOCAL &&
>   			    (contained || strset_contains(update_refs,
>   							  decoration->name))) {
> -				printf("update %s %s %s\n",
> -				       decoration->name,
> -				       oid_to_hex(&last_commit->object.oid),
> -				       oid_to_hex(&commit->object.oid));
> +				if (output_commands) {
> +					printf("update %s %s %s\n",
> +					       decoration->name,
> +					       oid_to_hex(&last_commit->object.oid),
> +					       oid_to_hex(&commit->object.oid));
> +				} else if (add_ref_to_transaction(transaction, decoration->name,
> +								  &last_commit->object.oid,
> +								  &commit->object.oid,
> +								  &transaction_err) < 0) {
> +					ret = error(_("failed to add ref update to transaction: %s"), transaction_err.buf);
> +					goto cleanup;
> +				}
>   			}

The lines here are very long due to the indentation, having a separate function to update the refs or print the ref updates would be much more readable.

Show 23 quoted lines
>   			decoration = decoration->next;
>   		}
> @@ -445,10 +500,33 @@ int cmd_replay(int argc,
>   
>   	/* In --advance mode, advance the target ref */
>   	if (result.clean == 1 && advance_name) {
> -		printf("update %s %s %s\n",
> -		       advance_name,
> -		       oid_to_hex(&last_commit->object.oid),
> -		       oid_to_hex(&onto->object.oid));
> +		if (output_commands) {
> +			printf("update %s %s %s\n",
> +			       advance_name,
> +			       oid_to_hex(&last_commit->object.oid),
> +			       oid_to_hex(&onto->object.oid));
> +		} else if (add_ref_to_transaction(transaction, advance_name,
> +						  &last_commit->object.oid,
> +						  &onto->object.oid,
> +						  &transaction_err) < 0) {
> +			ret = error(_("failed to add ref update to transaction: %s"), transaction_err.buf);
> +			goto cleanup;
> +		}
> +	}

Putting the code to update the refs or print the ref updates into a single function would avoid this duplication and over-long lines.

Thanks
Phillip
Show 137 quoted lines
> +	/* Commit the ref transaction if we have one */
> +	if (transaction && result.clean == 1) {
> +		if (ref_transaction_commit(transaction, &transaction_err)) {
> +			if (allow_partial) {
> +				warning(_("some ref updates failed: %s"), transaction_err.buf);
> +				ref_transaction_for_each_rejected_update(transaction,
> +									 print_rejected_update, NULL);
> +				ret = 0; /* Set failure even with allow_partial */
> +			} else {
> +				ret = error(_("failed to update refs: %s"), transaction_err.buf);
> +				goto cleanup;
> +			}
> +		}
>   	}
>   
>   	merge_finalize(&merge_opt, &result);
> @@ -457,9 +535,17 @@ int cmd_replay(int argc,
>   		strset_clear(update_refs);
>   		free(update_refs);
>   	}
> -	ret = result.clean;
> +
> +	/* Handle empty ranges: if no commits were processed, treat as success */
> +	if (!commits_processed)
> +		ret = 1; /* Success - no commits to replay is not an error */
> +	else
> +		ret = result.clean;
>   
>   cleanup:
> +	if (transaction)
> +		ref_transaction_free(transaction);
> +	strbuf_release(&transaction_err);
>   	release_revisions(&revs);
>   	free(advance_name);
>   
> diff --git a/t/t3650-replay-basics.sh b/t/t3650-replay-basics.sh
> index 58b3759935..8b4301e227 100755
> --- a/t/t3650-replay-basics.sh
> +++ b/t/t3650-replay-basics.sh
> @@ -52,7 +52,7 @@ test_expect_success 'setup bare' '
>   '
>   
>   test_expect_success 'using replay to rebase two branches, one on top of other' '
> -	git replay --onto main topic1..topic2 >result &&
> +	git replay --output-commands --onto main topic1..topic2 >result &&
>   
>   	test_line_count = 1 result &&
>   
> @@ -67,9 +67,30 @@ test_expect_success 'using replay to rebase two branches, one on top of other' '
>   	test_cmp expect result
>   '
>   
> +test_expect_success 'using replay with default atomic behavior (no output)' '
> +	# Create a test branch that wont interfere with others
> +	git branch atomic-test topic2 &&
> +	git rev-parse atomic-test >atomic-test-old &&
> +
> +	# Default behavior: atomic ref updates (no output)
> +	git replay --onto main topic1..atomic-test >output &&
> +	test_must_be_empty output &&
> +
> +	# Verify the branch was updated
> +	git rev-parse atomic-test >atomic-test-new &&
> +	! test_cmp atomic-test-old atomic-test-new &&
> +
> +	# Verify the history is correct
> +	git log --format=%s atomic-test >actual &&
> +	test_write_lines E D M L B A >expect &&
> +	test_cmp expect actual
> +'
> +
>   test_expect_success 'using replay on bare repo to rebase two branches, one on top of other' '
> -	git -C bare replay --onto main topic1..topic2 >result-bare &&
> -	test_cmp expect result-bare
> +	git -C bare replay --output-commands --onto main topic1..topic2 >result-bare &&
> +
> +	# The result should match what we got from the regular repo
> +	test_cmp result result-bare
>   '
>   
>   test_expect_success 'using replay to rebase with a conflict' '
> @@ -86,7 +107,7 @@ test_expect_success 'using replay to perform basic cherry-pick' '
>   	# 2nd field of result is refs/heads/main vs. refs/heads/topic2
>   	# 4th field of result is hash for main instead of hash for topic2
>   
> -	git replay --advance main topic1..topic2 >result &&
> +	git replay --output-commands --advance main topic1..topic2 >result &&
>   
>   	test_line_count = 1 result &&
>   
> @@ -102,7 +123,7 @@ test_expect_success 'using replay to perform basic cherry-pick' '
>   '
>   
>   test_expect_success 'using replay on bare repo to perform basic cherry-pick' '
> -	git -C bare replay --advance main topic1..topic2 >result-bare &&
> +	git -C bare replay --output-commands --advance main topic1..topic2 >result-bare &&
>   	test_cmp expect result-bare
>   '
>   
> @@ -115,7 +136,7 @@ test_expect_success 'replay fails when both --advance and --onto are omitted' '
>   '
>   
>   test_expect_success 'using replay to also rebase a contained branch' '
> -	git replay --contained --onto main main..topic3 >result &&
> +	git replay --output-commands --contained --onto main main..topic3 >result &&
>   
>   	test_line_count = 2 result &&
>   	cut -f 3 -d " " result >new-branch-tips &&
> @@ -139,12 +160,12 @@ test_expect_success 'using replay to also rebase a contained branch' '
>   '
>   
>   test_expect_success 'using replay on bare repo to also rebase a contained branch' '
> -	git -C bare replay --contained --onto main main..topic3 >result-bare &&
> +	git -C bare replay --output-commands --contained --onto main main..topic3 >result-bare &&
>   	test_cmp expect result-bare
>   '
>   
>   test_expect_success 'using replay to rebase multiple divergent branches' '
> -	git replay --onto main ^topic1 topic2 topic4 >result &&
> +	git replay --output-commands --onto main ^topic1 topic2 topic4 >result &&
>   
>   	test_line_count = 2 result &&
>   	cut -f 3 -d " " result >new-branch-tips &&
> @@ -168,7 +189,7 @@ test_expect_success 'using replay to rebase multiple divergent branches' '
>   '
>   
>   test_expect_success 'using replay on bare repo to rebase multiple divergent branches, including contained ones' '
> -	git -C bare replay --contained --onto main ^main topic2 topic3 topic4 >result &&
> +	git -C bare replay --output-commands --contained --onto main ^main topic2 topic3 topic4 >result &&
>   
>   	test_line_count = 4 result &&
>   	cut -f 3 -d " " result >new-branch-tips &&
> @@ -217,4 +238,131 @@ test_expect_success 'merge.directoryRenames=false' '
>   		--onto rename-onto rename-onto..rename-from
>   '
>   
> +# Tests for new default atomic behavior and options> > +test_expect_success 'replay default behavior should not produce 
output when successful' '
Show 125 quoted lines
> +	git replay --onto main topic1..topic3 >output &&
> +	test_must_be_empty output
> +'
> +
> +test_expect_success 'replay with --output-commands produces traditional output' '
> +	git replay --output-commands --onto main topic1..topic3 >output &&
> +	test_line_count = 1 output &&
> +	grep "^update refs/heads/topic3 " output
> +'
> +
> +test_expect_success 'replay with --allow-partial should not produce output when successful' '
> +	git replay --allow-partial --onto main topic1..topic3 >output &&
> +	test_must_be_empty output
> +'
> +
> +test_expect_success 'replay fails when --output-commands and --allow-partial are used together' '
> +	test_must_fail git replay --output-commands --allow-partial --onto main topic1..topic2 2>error &&
> +	grep "cannot be used together" error
> +'
> +
> +test_expect_success 'replay with --contained updates multiple branches atomically' '
> +	# Create fresh test branches based on the original structure
> +	# contained-topic1 should be contained within the range to contained-topic3
> +	git branch contained-base main &&
> +	git checkout -b contained-topic1 contained-base &&
> +	test_commit ContainedC &&
> +	git checkout -b contained-topic3 contained-topic1 &&
> +	test_commit ContainedG &&
> +	test_commit ContainedH &&
> +	git checkout main &&
> +
> +	# Store original states
> +	git rev-parse contained-topic1 >contained-topic1-old &&
> +	git rev-parse contained-topic3 >contained-topic3-old &&
> +
> +	# Use --contained to update multiple branches - this should update both
> +	git replay --contained --onto main contained-base..contained-topic3 &&
> +
> +	# Verify both branches were updated
> +	git rev-parse contained-topic1 >contained-topic1-new &&
> +	git rev-parse contained-topic3 >contained-topic3-new &&
> +	! test_cmp contained-topic1-old contained-topic1-new &&
> +	! test_cmp contained-topic3-old contained-topic3-new
> +'
> +
> +test_expect_success 'replay atomic behavior: all refs updated or none' '
> +	# Store original state
> +	git rev-parse topic4 >topic4-old &&
> +
> +	# Default atomic behavior
> +	git replay --onto main main..topic4 &&
> +
> +	# Verify ref was updated
> +	git rev-parse topic4 >topic4-new &&
> +	! test_cmp topic4-old topic4-new &&
> +
> +	# Verify no partial state
> +	git log --format=%s topic4 >actual &&
> +	test_write_lines J I M L B A >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'replay works correctly with bare repositories' '
> +	# Test atomic behavior in bare repo (important for Gitaly)
> +	git checkout -b bare-test topic1 &&
> +	test_commit BareTest &&
> +
> +	# Test with bare repo - replay the commits from main..bare-test to get the full history
> +	git -C bare fetch .. bare-test:bare-test &&
> +	git -C bare replay --onto main main..bare-test &&
> +
> +	# Verify the bare repo was updated correctly (no output)
> +	git -C bare log --format=%s bare-test >actual &&
> +	test_write_lines BareTest F C M L B A >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'replay --allow-partial with no failures produces no output' '
> +	git checkout -b partial-test topic1 &&
> +	test_commit PartialTest &&
> +
> +	# Should succeed silently even with partial mode
> +	git replay --allow-partial --onto main topic1..partial-test >output &&
> +	test_must_be_empty output
> +'
> +
> +test_expect_success 'replay maintains ref update consistency' '
> +	# Test that traditional vs atomic produce equivalent results
> +	git checkout -b method1-test topic2 &&
> +	git checkout -b method2-test topic2 &&
> +
> +	# Both methods should update refs to point to the same replayed commits
> +	git replay --output-commands --onto main topic1..method1-test >update-commands &&
> +	git update-ref --stdin <update-commands &&
> +	git log --format=%s method1-test >traditional-result &&
> +
> +	# Direct atomic method should produce same commit history
> +	git replay --onto main topic1..method2-test &&
> +	git log --format=%s method2-test >atomic-result &&
> +
> +	# Both methods should produce identical commit histories
> +	test_cmp traditional-result atomic-result
> +'
> +
> +test_expect_success 'replay error messages are helpful and clear' '
> +	# Test that error messages are clear
> +	test_must_fail git replay --output-commands --allow-partial --onto main topic1..topic2 2>error &&
> +	grep "cannot be used together" error
> +'
> +
> +test_expect_success 'replay with empty range produces no output and no changes' '
> +	# Create a test branch for empty range testing
> +	git checkout -b empty-test topic1 &&
> +	git rev-parse empty-test >empty-test-before &&
> +
> +	# Empty range should succeed but do nothing
> +	git replay --onto main empty-test..empty-test >output &&
> +	test_must_be_empty output &&
> +
> +	# Branch should be unchanged
> +	git rev-parse empty-test >empty-test-after &&
> +	test_cmp empty-test-before empty-test-after
> +'
> +
>   test_done
Previous: Christian CouderNext: Karthik Nayak
Message 33 of 125 in “replay: add --update-refs option”
  1. 0/2 replay: add --update-refs optionSiddharth Asthana, Sep 8, 2025
  2. 1/2 replay: add --update-refs optionSiddharth Asthana, Sep 8, 2025
  3. Patrick SteinhardtSep 8, 2025
  4. Siddharth AsthanaSep 9, 2025
  5. Patrick SteinhardtSep 9, 2025
  6. Elijah NewrenSep 9, 2025
  7. Siddharth AsthanaSep 10, 2025
  8. 2/2 replay: document --update-refs and --batch optionsSiddharth Asthana, Sep 8, 2025
  9. Christian CouderSep 8, 2025
  10. Siddharth AsthanaSep 9, 2025
  11. Christian CouderSep 9, 2025
  12. Siddharth AsthanaSep 10, 2025
  13. Kristoffer HaugsbakkSep 8, 2025
  14. Siddharth AsthanaSep 9, 2025
  15. Andrei RybakSep 9, 2025
  16. Siddharth AsthanaSep 10, 2025
  17. Christian CouderSep 8, 2025
  18. Siddharth AsthanaSep 9, 2025
  19. Kristoffer HaugsbakkSep 8, 2025
  20. Siddharth AsthanaSep 9, 2025
  21. Elijah NewrenSep 9, 2025
  22. Christian CouderSep 9, 2025
  23. Elijah NewrenSep 9, 2025
  24. Junio C HamanoSep 9, 2025
  25. Elijah NewrenSep 9, 2025
  26. 0/1 replay: make atomic ref updates the default behaviorSiddharth Asthana, Sep 26, 2025
  27. 1/1 replay: make atomic ref updates the default behaviorSiddharth Asthana, Sep 26, 2025
  28. Christian CouderSep 30, 2025
  29. Siddharth AsthanaOct 2, 2025
  30. Christian CouderOct 3, 2025
  31. Elijah NewrenOct 2, 2025
  32. Christian CouderOct 3, 2025
  33. Phillip WoodSep 30, 2025
  34. Karthik NayakOct 2, 2025
  35. Siddharth AsthanaOct 2, 2025
  36. Siddharth AsthanaOct 2, 2025
  37. Phillip WoodOct 8, 2025
  38. Siddharth AsthanaOct 8, 2025
  39. Elijah NewrenOct 8, 2025
  40. Siddharth AsthanaOct 8, 2025
  41. Phillip WoodOct 9, 2025
  42. Elijah NewrenOct 2, 2025
  43. Junio C HamanoOct 2, 2025
  44. Siddharth AsthanaOct 2, 2025
  45. Siddharth AsthanaOct 2, 2025
  46. Christian CouderOct 3, 2025
  47. Siddharth AsthanaOct 8, 2025
  48. Elijah NewrenOct 3, 2025
  49. Junio C HamanoOct 3, 2025
  50. Siddharth AsthanaOct 8, 2025
  51. Junio C HamanoOct 8, 2025
  52. Siddharth AsthanaOct 8, 2025
  53. Elijah NewrenOct 8, 2025
  54. Siddharth AsthanaOct 8, 2025
  55. Kristoffer HaugsbakkOct 2, 2025
  56. Siddharth AsthanaOct 2, 2025
  57. Kristoffer HaugsbakkOct 3, 2025
  58. Siddharth AsthanaOct 8, 2025
  59. Elijah NewrenOct 8, 2025
  60. Kristoffer HaugsbakkOct 8, 2025
  61. Siddharth AsthanaOct 8, 2025
  62. 0/3 replay: make atomic ref updates the defaultSiddharth Asthana, Oct 13, 2025
  63. 1/3 replay: use die_for_incompatible_opt2() for option validationSiddharth Asthana, Oct 13, 2025
  64. 2/3 replay: make atomic ref updates the default behaviorSiddharth Asthana, Oct 13, 2025
  65. Junio C HamanoOct 13, 2025
  66. Siddharth AsthanaOct 15, 2025
  67. 3/3 replay: add replay.defaultAction config optionSiddharth Asthana, Oct 13, 2025
  68. Junio C HamanoOct 13, 2025
  69. Siddharth AsthanaOct 15, 2025
  70. Christian CouderOct 15, 2025
  71. Junio C HamanoOct 15, 2025
  72. 0/3 replay: make atomic ref updates the defaultSiddharth Asthana, Oct 22, 2025
  73. 1/3 replay: use die_for_incompatible_opt2() for option validationSiddharth Asthana, Oct 22, 2025
  74. 2/3 replay: make atomic ref updates the default behaviorSiddharth Asthana, Oct 22, 2025
  75. Junio C HamanoOct 22, 2025
  76. Siddharth AsthanaOct 28, 2025
  77. Christian CouderOct 24, 2025
  78. Junio C HamanoOct 24, 2025
  79. Siddharth AsthanaOct 28, 2025
  80. Siddharth AsthanaOct 28, 2025
  81. 3/3 replay: add replay.refAction config optionSiddharth Asthana, Oct 22, 2025
  82. Christian CouderOct 24, 2025
  83. Junio C HamanoOct 24, 2025
  84. Siddharth AsthanaOct 28, 2025
  85. Siddharth AsthanaOct 28, 2025
  86. Phillip WoodOct 24, 2025
  87. Phillip WoodOct 24, 2025
  88. Siddharth AsthanaOct 28, 2025
  89. Siddharth AsthanaOct 28, 2025
  90. Junio C HamanoOct 23, 2025
  91. Junio C HamanoOct 25, 2025
  92. Siddharth AsthanaOct 28, 2025
  93. Christian CouderOct 24, 2025
  94. 0/3 replay: make atomic ref updates the defaultSiddharth Asthana, Oct 28, 2025
  95. 1/3 replay: use die_for_incompatible_opt2() for option validationSiddharth Asthana, Oct 28, 2025
  96. 2/3 replay: make atomic ref updates the default behaviorSiddharth Asthana, Oct 28, 2025
  97. 3/3 replay: add replay.refAction config optionSiddharth Asthana, Oct 28, 2025
  98. Christian CouderOct 29, 2025
  99. Siddharth AsthanaOct 29, 2025
  100. 0/3 replay: make atomic ref updates the defaultSiddharth Asthana, Oct 30, 2025
  101. 1/3 replay: use die_for_incompatible_opt2() for option validationSiddharth Asthana, Oct 30, 2025
  102. Elijah NewrenOct 31, 2025
  103. Siddharth AsthanaNov 5, 2025
  104. 2/3 replay: make atomic ref updates the default behaviorSiddharth Asthana, Oct 30, 2025
  105. Elijah NewrenOct 31, 2025
  106. Junio C HamanoOct 31, 2025
  107. Siddharth AsthanaNov 5, 2025
  108. Phillip WoodNov 3, 2025
  109. Siddharth AsthanaNov 3, 2025
  110. Phillip WoodNov 4, 2025
  111. 3/3 replay: add replay.refAction config optionSiddharth Asthana, Oct 30, 2025
  112. Christian CouderOct 31, 2025
  113. Siddharth AsthanaNov 5, 2025
  114. Elijah NewrenOct 31, 2025
  115. Siddharth AsthanaNov 5, 2025
  116. Elijah NewrenOct 31, 2025
  117. 0/3 replay: make atomic ref updates the defaultSiddharth Asthana, Nov 5, 2025
  118. 1/3 replay: use die_for_incompatible_opt2() for option validationSiddharth Asthana, Nov 5, 2025
  119. 2/3 replay: make atomic ref updates the default behaviorSiddharth Asthana, Nov 5, 2025
  120. 3/3 replay: add replay.refAction config optionSiddharth Asthana, Nov 5, 2025
  121. Elijah NewrenNov 6, 2025
  122. Siddharth AsthanaNov 8, 2025
  123. Elijah NewrenNov 8, 2025
  124. Phillip WoodNov 7, 2025
  125. Siddharth AsthanaNov 8, 2025

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