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[PATCH 2/4] branch: refactor out branch validation from create_branch()

From
Glen Choo <chooglen@google.com>
Date
Nov 22, 2021, 22:32 UTC
Message-ID
<20211122223252.19922-3-chooglen@google.com>
In-Reply-To
<20211122223252.19922-1-chooglen@google.com>

In a subsequent commit, we would like to be able to validate whether or not a branch name is valid before we create it (--dry-run). This is useful for `git branch --recurse-submodules topic` because it allows Git to determine if the branch 'topic' can be created in all submodules without creating the branch 'topic'.

A good starting point would be to refactor out the start point validation and dwim logic in create_branch() in a validate_branch_start() helper function. Once we do so, it becomes clear that create_branch() is more complex than it needs to be - create_branch() is also used to set tracking information when performing `git branch --set-upstream-to`. This made more sense when (the now unsupported) --set-upstream was first introduced in 4fc5006676 (Add branch --set-upstream, 2010-01-18), because it would sometimes create a branch and sometimes update tracking information without creating a branch.

Refactor out the branch validation and dwim logic from create_branch() into validate_branch_start(), make it so that create_branch() always tries to create a branch, and replace the now-incorrect create_branch() call with setup_tracking(). Since there were none, add tests for creating a branch with `--force`.

Signed-off-by: Glen Choo <chooglen@google.com>
---
In this refactor, I preserved the existing behavior by making
setup_tracking() call validate_branch_start(). setup_tracking() needs
the dwim behavior e.g. to expand 'origin/main' into
'refs/remotes/origin/main' but I'm doubtful that it needs the exact same
set of validation behavior as creating a new branch e.g. validating that
the object_id is a commit.
 branch.c          | 177 ++++++++++++++++++++++++----------------------
 branch.h          |  13 +++-
 builtin/branch.c  |   7 +-
 t/t3200-branch.sh |  17 +++++
 4 files changed, 121 insertions(+), 93 deletions(-)
diff --git a/branch.c b/branch.c
index 07a46430b3..f8b755513f 100644
--- a/branch.c
+++ b/branch.c
@@ -126,43 +126,6 @@ int install_branch_config(int flag, const char *local, const char *origin, const
 	return -1;
 }
 
-/*
- * This is called when new_ref is branched off of orig_ref, and tries
- * to infer the settings for branch.<new_ref>.{remote,merge} from the
- * config.
- */
-static void setup_tracking(const char *new_ref, const char *orig_ref,
-			   enum branch_track track, int quiet)
-{
-	struct tracking tracking;
-	int config_flags = quiet ? 0 : BRANCH_CONFIG_VERBOSE;
-
-	memset(&tracking, 0, sizeof(tracking));
-	tracking.spec.dst = (char *)orig_ref;
-	if (for_each_remote(find_tracked_branch, &tracking))
-		return;
-
-	if (!tracking.matches)
-		switch (track) {
-		case BRANCH_TRACK_ALWAYS:
-		case BRANCH_TRACK_EXPLICIT:
-		case BRANCH_TRACK_OVERRIDE:
-			break;
-		default:
-			return;
-		}
-
-	if (tracking.matches > 1)
-		die(_("Not tracking: ambiguous information for ref %s"),
-		    orig_ref);
-
-	if (install_branch_config(config_flags, new_ref, tracking.remote,
-			      tracking.src ? tracking.src : orig_ref) < 0)
-		exit(-1);
-
-	free(tracking.src);
-}
-
 int read_branch_desc(struct strbuf *buf, const char *branch_name)
 {
 	char *v = NULL;
@@ -243,33 +206,17 @@ N_("\n"
 "will track its remote counterpart, you may want to use\n"
 "\"git push -u\" to set the upstream config as you push.");
 
-void create_branch(struct repository *r,
-		   const char *name, const char *start_name,
-		   int force, int clobber_head_ok, int reflog,
-		   int quiet, enum branch_track track)
+static void validate_branch_start(struct repository *r, const char *start_name,
+				  enum branch_track track,
+				  struct object_id *oid, char **full_ref)
 {
 	struct commit *commit;
-	struct object_id oid;
-	char *real_ref;
-	struct strbuf ref = STRBUF_INIT;
-	int forcing = 0;
-	int dont_change_ref = 0;
 	int explicit_tracking = 0;
 
 	if (track == BRANCH_TRACK_EXPLICIT || track == BRANCH_TRACK_OVERRIDE)
 		explicit_tracking = 1;
 
-	if ((track == BRANCH_TRACK_OVERRIDE || clobber_head_ok)
-	    ? validate_branchname(name, &ref)
-	    : validate_new_branchname(name, &ref, force)) {
-		if (!force)
-			dont_change_ref = 1;
-		else
-			forcing = 1;
-	}
-
-	real_ref = NULL;
-	if (get_oid_mb(start_name, &oid)) {
+	if (repo_get_oid_mb(r, start_name, oid)) {
 		if (explicit_tracking) {
 			if (advice_enabled(ADVICE_SET_UPSTREAM_FAILURE)) {
 				error(_(upstream_missing), start_name);
@@ -281,7 +228,8 @@ void create_branch(struct repository *r,
 		die(_("Not a valid object name: '%s'."), start_name);
 	}
 
-	switch (dwim_ref(start_name, strlen(start_name), &oid, &real_ref, 0)) {
+	switch (repo_dwim_ref(r, start_name, strlen(start_name), oid, full_ref,
+			      0)) {
 	case 0:
 		/* Not branching from any existing branch */
 		if (explicit_tracking)
@@ -289,12 +237,12 @@ void create_branch(struct repository *r,
 		break;
 	case 1:
 		/* Unique completion -- good, only if it is a real branch */
-		if (!starts_with(real_ref, "refs/heads/") &&
-		    validate_remote_tracking_branch(real_ref)) {
+		if (!starts_with(*full_ref, "refs/heads/") &&
+		    validate_remote_tracking_branch(*full_ref)) {
 			if (explicit_tracking)
 				die(_(upstream_not_branch), start_name);
 			else
-				FREE_AND_NULL(real_ref);
+				FREE_AND_NULL(*full_ref);
 		}
 		break;
 	default:
@@ -302,37 +250,96 @@ void create_branch(struct repository *r,
 		break;
 	}
 
-	if ((commit = lookup_commit_reference(r, &oid)) == NULL)
+	if ((commit = lookup_commit_reference(r, oid)) == NULL)
 		die(_("Not a valid branch point: '%s'."), start_name);
-	oidcpy(&oid, &commit->object.oid);
+	oidcpy(oid, &commit->object.oid);
+}
+
+void setup_tracking(const char *new_ref, const char *orig_ref,
+			   enum branch_track track, int quiet, int expand_orig)
+{
+	struct tracking tracking;
+	int config_flags = quiet ? 0 : BRANCH_CONFIG_VERBOSE;
+	char *full_orig_ref;
+	struct object_id unused_oid;
+
+	memset(&tracking, 0, sizeof(tracking));
+	if (expand_orig)
+		validate_branch_start(the_repository, orig_ref, track, &unused_oid, &full_orig_ref);
+	else
+		full_orig_ref = xstrdup(orig_ref);
+
+	tracking.spec.dst = full_orig_ref;
+	if (for_each_remote(find_tracked_branch, &tracking))
+		goto cleanup;
+
+	if (!tracking.matches)
+		switch (track) {
+		case BRANCH_TRACK_ALWAYS:
+		case BRANCH_TRACK_EXPLICIT:
+		case BRANCH_TRACK_OVERRIDE:
+			break;
+		default:
+			goto cleanup;
+		}
+
+	if (tracking.matches > 1)
+		die(_("Not tracking: ambiguous information for ref %s"),
+		    full_orig_ref);
+
+	if (install_branch_config(config_flags, new_ref, tracking.remote,
+			      tracking.src ? tracking.src : full_orig_ref) < 0)
+		exit(-1);
+
+cleanup:
+	free(tracking.src);
+	free(full_orig_ref);
+}
+
+void create_branch(struct repository *r, const char *name,
+		   const char *start_name, int force, int clobber_head_ok,
+		   int reflog, int quiet, enum branch_track track)
+{
+	struct object_id oid;
+	char *real_ref;
+	struct strbuf ref = STRBUF_INIT;
+	int forcing = 0;
+	struct ref_transaction *transaction;
+	struct strbuf err = STRBUF_INIT;
+	char *msg;
+
+	if (clobber_head_ok && !force)
+		BUG("'clobber_head_ok' can only be used with 'force'");
+
+	if (clobber_head_ok ?
+			  validate_branchname(name, &ref) :
+			  validate_new_branchname(name, &ref, force)) {
+		forcing = 1;
+	}
+
+	validate_branch_start(r, start_name, track, &oid, &real_ref);
 
 	if (reflog)
 		log_all_ref_updates = LOG_REFS_NORMAL;
 
-	if (!dont_change_ref) {
-		struct ref_transaction *transaction;
-		struct strbuf err = STRBUF_INIT;
-		char *msg;
-
-		if (forcing)
-			msg = xstrfmt("branch: Reset to %s", start_name);
-		else
-			msg = xstrfmt("branch: Created from %s", start_name);
-
-		transaction = ref_transaction_begin(&err);
-		if (!transaction ||
-		    ref_transaction_update(transaction, ref.buf,
-					   &oid, forcing ? NULL : null_oid(),
-					   0, msg, &err) ||
-		    ref_transaction_commit(transaction, &err))
-			die("%s", err.buf);
-		ref_transaction_free(transaction);
-		strbuf_release(&err);
-		free(msg);
-	}
+	if (forcing)
+		msg = xstrfmt("branch: Reset to %s", start_name);
+	else
+		msg = xstrfmt("branch: Created from %s", start_name);
+
+	transaction = ref_transaction_begin(&err);
+	if (!transaction ||
+		ref_transaction_update(transaction, ref.buf,
+					&oid, forcing ? NULL : null_oid(),
+					0, msg, &err) ||
+		ref_transaction_commit(transaction, &err))
+		die("%s", err.buf);
+	ref_transaction_free(transaction);
+	strbuf_release(&err);
+	free(msg);
 
 	if (real_ref && track)
-		setup_tracking(ref.buf + 11, real_ref, track, quiet);
+		setup_tracking(ref.buf + 11, real_ref, track, quiet, 0);
 
 	strbuf_release(&ref);
 	free(real_ref);
diff --git a/branch.h b/branch.h
index df0be61506..75cefcdcbd 100644
--- a/branch.h
+++ b/branch.h
@@ -17,6 +17,15 @@ extern enum branch_track git_branch_track;
 
 /* Functions for acting on the information about branches. */
 
+/*
+ * This sets the branch.<new_ref>.{remote,merge} config settings so that
+ * branch 'new_ref' tracks 'orig_ref'. This is called when branches are
+ * created, or when branch configs are updated (e.g. with
+ * git branch --set-upstream-to).
+ */
+void setup_tracking(const char *new_ref, const char *orig_ref,
+		    enum branch_track track, int quiet, int expand_orig);
+
 /*
  * Creates a new branch, where:
  *
@@ -29,8 +38,8 @@ extern enum branch_track git_branch_track;
  *
  *   - force enables overwriting an existing (non-head) branch
  *
- *   - clobber_head_ok allows the currently checked out (hence existing)
- *     branch to be overwritten; without 'force', it has no effect.
+ *   - clobber_head_ok, when enabled with 'force', allows the currently
+ *     checked out (head) branch to be overwritten
  *
  *   - reflog creates a reflog for the branch
  *
diff --git a/builtin/branch.c b/builtin/branch.c
index 0b7ed82654..eb5c117a6e 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -820,12 +820,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		if (!ref_exists(branch->refname))
 			die(_("branch '%s' does not exist"), branch->name);
 
-		/*
-		 * create_branch takes care of setting up the tracking
-		 * info and making sure new_upstream is correct
-		 */
-		create_branch(the_repository, branch->name, new_upstream,
-			      0, 0, 0, quiet, BRANCH_TRACK_OVERRIDE);
+		setup_tracking(branch->name, new_upstream, BRANCH_TRACK_OVERRIDE, quiet, 1);
 	} else if (unset_upstream) {
 		struct branch *branch = branch_get(argv[0]);
 		struct strbuf buf = STRBUF_INIT;
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index e575ffb4ff..6bf95a1707 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -42,6 +42,23 @@ test_expect_success 'git branch abc should create a branch' '
 	git branch abc && test_path_is_file .git/refs/heads/abc
 '
 
+test_expect_success 'git branch abc should fail when abc exists' '
+	test_must_fail git branch abc
+'
+
+test_expect_success 'git branch --force abc should fail when abc is checked out' '
+	test_when_finished git switch main &&
+	git switch abc &&
+	test_must_fail git branch --force abc HEAD~1
+'
+
+test_expect_success 'git branch --force abc should succeed when abc exists' '
+	git rev-parse HEAD~1 >expect &&
+	git branch --force abc HEAD~1 &&
+	git rev-parse abc >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'git branch a/b/c should create a branch' '
 	git branch a/b/c && test_path_is_file .git/refs/heads/a/b/c
 '

-- 
2.33.GIT
Previous: Junio C HamanoNext: Glen Choo
Message 8 of 110 in “implement branch --recurse-submodules”
  1. 0/4 implement branch --recurse-submodulesGlen Choo, Nov 22, 2021
  2. 1/4 submodule-config: add submodules_of_tree() helperGlen Choo, Nov 22, 2021
  3. Jonathan TanNov 23, 2021
  4. Glen ChooNov 23, 2021
  5. Ævar Arnfjörð BjarmasonNov 23, 2021
  6. Glen ChooNov 23, 2021
  7. Junio C HamanoNov 23, 2021
  8. 2/4 branch: refactor out branch validation from create_branch()Glen Choo, Nov 22, 2021
  9. 3/4 branch: add --dry-run option to branchGlen Choo, Nov 22, 2021
  10. Ævar Arnfjörð BjarmasonNov 23, 2021
  11. Glen ChooNov 23, 2021
  12. Jonathan TanNov 23, 2021
  13. Glen ChooNov 24, 2021
  14. 4/4 branch: add --recurse-submodules option for branch creationGlen Choo, Nov 22, 2021
  15. Ævar Arnfjörð BjarmasonNov 23, 2021
  16. Glen ChooNov 23, 2021
  17. Philippe BlainNov 23, 2021
  18. Glen ChooNov 23, 2021
  19. Jonathan TanNov 24, 2021
  20. Glen ChooNov 24, 2021
  21. Jonathan TanNov 29, 2021
  22. 0/3 implement branch --recurse-submodulesGlen Choo, Dec 6, 2021
  23. 1/3 branch: move --set-upstream-to behavior to setup_tracking()Glen Choo, Dec 6, 2021
  24. Junio C HamanoDec 6, 2021
  25. Glen ChooDec 8, 2021
  26. Junio C HamanoDec 6, 2021
  27. Glen ChooDec 8, 2021
  28. 2/3 builtin/branch: clean up action-picking logic in cmd_branch()Glen Choo, Dec 6, 2021
  29. 3/3 branch: add --recurse-submodules option for branch creationGlen Choo, Dec 6, 2021
  30. 0/5 implement branch --recurse-submodulesGlen Choo, Dec 9, 2021
  31. 1/5 branch: move --set-upstream-to behavior to setup_tracking()Glen Choo, Dec 9, 2021
  32. Jonathan TanDec 9, 2021
  33. Glen ChooDec 9, 2021
  34. 2/5 branch: remove forward declaration of validate_branch_start()Glen Choo, Dec 9, 2021
  35. 3/5 builtin/branch: clean up action-picking logic in cmd_branch()Glen Choo, Dec 9, 2021
  36. Jonathan TanDec 9, 2021
  37. Glen ChooDec 9, 2021
  38. 4/5 branch: add --recurse-submodules option for branch creationGlen Choo, Dec 9, 2021
  39. Philippe BlainDec 11, 2021
  40. Glen ChooDec 14, 2021
  41. 5/5 branch.c: replace questionable exit() codesGlen Choo, Dec 9, 2021
  42. Ævar Arnfjörð BjarmasonDec 10, 2021
  43. Glen ChooDec 10, 2021
  44. Junio C HamanoDec 13, 2021
  45. Ævar Arnfjörð BjarmasonDec 13, 2021
  46. Junio C HamanoDec 13, 2021
  47. Jonathan TanDec 9, 2021
  48. Glen ChooDec 9, 2021
  49. Jonathan TanDec 13, 2021
  50. Glen ChooDec 14, 2021
  51. 0/5 implement branch --recurse-submodulesGlen Choo, Dec 16, 2021
  52. 1/5 branch: move --set-upstream-to behavior to dwim_and_setup_tracking()Glen Choo, Dec 16, 2021
  53. 2/5 branch: make create_branch() always create a branchGlen Choo, Dec 16, 2021
  54. 3/5 branch: add a dry_run parameter to create_branch()Glen Choo, Dec 16, 2021
  55. 4/5 builtin/branch: clean up action-picking logic in cmd_branch()Glen Choo, Dec 16, 2021
  56. 5/5 branch: add --recurse-submodules option for branch creationGlen Choo, Dec 16, 2021
  57. 0/5 implement branch --recurse-submodulesGlen Choo, Dec 16, 2021
  58. 1/5 branch: move --set-upstream-to behavior to dwim_and_setup_tracking()Glen Choo, Dec 16, 2021
  59. 2/5 branch: make create_branch() always create a branchGlen Choo, Dec 16, 2021
  60. 3/5 branch: add a dry_run parameter to create_branch()Glen Choo, Dec 16, 2021
  61. 4/5 builtin/branch: clean up action-picking logic in cmd_branch()Glen Choo, Dec 16, 2021
  62. 5/5 branch: add --recurse-submodules option for branch creationGlen Choo, Dec 16, 2021
  63. Junio C HamanoDec 17, 2021
  64. Junio C HamanoDec 17, 2021
  65. Glen ChooDec 20, 2021
  66. Junio C HamanoDec 20, 2021
  67. Glen ChooDec 20, 2021
  68. 0/5 implement branch --recurse-submodulesGlen Choo, Dec 20, 2021
  69. 1/5 branch: move --set-upstream-to behavior to dwim_and_setup_tracking()Glen Choo, Dec 20, 2021
  70. Jonathan TanJan 11, 2022
  71. Glen ChooJan 11, 2022
  72. Jonathan TanJan 11, 2022
  73. 2/5 branch: make create_branch() always create a branchGlen Choo, Dec 20, 2021
  74. Jonathan TanJan 11, 2022
  75. Glen ChooJan 11, 2022
  76. 3/5 branch: add a dry_run parameter to create_branch()Glen Choo, Dec 20, 2021
  77. 4/5 builtin/branch: clean up action-picking logic in cmd_branch()Glen Choo, Dec 20, 2021
  78. 5/5 branch: add --recurse-submodules option for branch creationGlen Choo, Dec 20, 2021
  79. Junio C HamanoDec 26, 2021
  80. Jonathan TanJan 11, 2022
  81. Glen ChooJan 11, 2022
  82. Jonathan TanJan 11, 2022
  83. Glen ChooJan 11, 2022
  84. Glen ChooDec 20, 2021
  85. Junio C HamanoDec 21, 2021
  86. Glen ChooDec 21, 2021
  87. 0/6 implement branch --recurse-submodulesGlen Choo, Jan 24, 2022
  88. 2/6 branch: make create_branch() always create a branchGlen Choo, Jan 24, 2022
  89. 1/6 branch: move --set-upstream-to behavior to dwim_and_setup_tracking()Glen Choo, Jan 24, 2022
  90. 3/6 branch: add a dry_run parameter to create_branch()Glen Choo, Jan 24, 2022
  91. 4/6 builtin/branch: consolidate action-picking logic in cmd_branch()Glen Choo, Jan 24, 2022
  92. 5/6 branch: add --recurse-submodules option for branch creationGlen Choo, Jan 24, 2022
  93. Jonathan TanJan 27, 2022
  94. Glen ChooJan 27, 2022
  95. Glen ChooJan 27, 2022
  96. 6/6 branch.c: use 'goto cleanup' in setup_tracking() to fix memory leaksGlen Choo, Jan 24, 2022
  97. Junio C HamanoJan 27, 2022
  98. Glen ChooJan 28, 2022
  99. 0/6 implement branch --recurse-submodulesGlen Choo, Jan 29, 2022
  100. 1/6 branch: move --set-upstream-to behavior to dwim_and_setup_tracking()Glen Choo, Jan 29, 2022
  101. 2/6 branch: make create_branch() always create a branchGlen Choo, Jan 29, 2022
  102. Junio C HamanoFeb 1, 2022
  103. 3/6 branch: add a dry_run parameter to create_branch()Glen Choo, Jan 29, 2022
  104. 4/6 builtin/branch: consolidate action-picking logic in cmd_branch()Glen Choo, Jan 29, 2022
  105. 5/6 branch: add --recurse-submodules option for branch creationGlen Choo, Jan 29, 2022
  106. Glen ChooFeb 4, 2022
  107. Junio C HamanoFeb 4, 2022
  108. Glen ChooFeb 4, 2022
  109. 6/6 branch.c: use 'goto cleanup' in setup_tracking() to fix memory leaksGlen Choo, Jan 29, 2022
  110. Jonathan TanFeb 1, 2022

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