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[PATCH 2/2] checkout: die() on ambiguous tracking branches

From
AGAlexandr Miloslavskiy via GitGitGadget <gitgitgadget@gmail.com>
Date
Nov 27, 2019, 09:48 UTC
Message-ID
<7dde1a3b4e4e76cd1a820b5277f694fdfad3a922.1574848137.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.477.git.1574848137.gitgitgadget@gmail.com>
From: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>

Before this patch, when there were multiple DWIM candidates for remote branch, git decided to try the argument as pathspec instead. I believe that such behavior is a surprise: adding another remote suddenly causes git to discard file contents, because it was unsure which branch to pick. There was an incomplete attempt to prevent that in [3].

I understand that this was never intended:
  [1] introduces the unexpected behavior. Before, there was fallback
  from not-a-ref to pathspec. This is reasonable DWIM. After, there is
  another fallback from ambiguous-remote to pathspec. I understand that
  it was kind of copy&paste oversight.
  [2] noticed the unexpected behavior but chose to semi-document it
  instead of forbidding, because the goal of the patch series was
  focused on something else.
  [3] adds `die()` when there is ambiguity between branch and file. The
  case of multiple tracking branches is seemingly overlooked.
Change to complain about ambiguity instead of doing unexpected things.
[1] Commit 70c9ac2f ("DWIM "git checkout frotz" to "git checkout -b frotz origin/frotz"" 2009-10-18)
    https://public-inbox.org/git/7vaazpxha4.fsf_-_@alter.siamese.dyndns.org/
[2] Commit ad8d5104 ("checkout: add advice for ambiguous "checkout <branch>"", 2018-06-05)
    https://public-inbox.org/git/20180502105452.17583-1-avarab@gmail.com/
[3] Commit be4908f1 ("checkout: disambiguate dwim tracking branches and local files", 2018-11-13)
    https://public-inbox.org/git/20181110120707.25846-1-pclouds@gmail.com/
Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
---
 builtin/checkout.c       | 56 ++++++++++++++++++----------------------
 t/t2024-checkout-dwim.sh | 23 +++++++++++++++--
 2 files changed, 46 insertions(+), 33 deletions(-)
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e1b9df1543..6fb427990f 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1115,10 +1115,10 @@ static void setup_new_branch_info_and_source_tree(
 
 static const char *parse_remote_branch(const char *arg,
 				       struct object_id *rev,
-				       int could_be_checkout_paths,
-				       int *dwim_remotes_matched)
+				       int could_be_checkout_paths)
 {
-	const char *remote = unique_tracking_name(arg, rev, dwim_remotes_matched);
+	int num_matches = 0;
+	const char *remote = unique_tracking_name(arg, rev, &num_matches);
 	
 	if (remote && could_be_checkout_paths) {
 		die(_("'%s' could be both a local file and a tracking branch.\n"
@@ -1126,6 +1126,22 @@ static const char *parse_remote_branch(const char *arg,
 		    arg);
 	}
 
+	if (!remote && (num_matches > 1)) {
+	    if (advice_checkout_ambiguous_remote_branch_name) {
+		    advise(_("If you meant to check out a remote tracking branch on, e.g. 'origin',\n"
+			     "you can do so by fully qualifying the name with the --track option:\n"
+			     "\n"
+			     "    git checkout --track origin/<name>\n"
+			     "\n"
+			     "If you'd like to always have checkouts of an ambiguous <name> prefer\n"
+			     "one remote, e.g. the 'origin' remote, consider setting\n"
+			     "checkout.defaultRemote=origin in your config."));
+	    }
+
+	    die(_("'%s' matched multiple (%d) remote tracking branches"),
+		arg, num_matches);
+	}
+
 	return remote;
 }
 
@@ -1133,8 +1149,7 @@ static int parse_branchname_arg(int argc, const char **argv,
 				int dwim_new_local_branch_ok,
 				struct branch_info *new_branch_info,
 				struct checkout_opts *opts,
-				struct object_id *rev,
-				int *dwim_remotes_matched)
+				struct object_id *rev)
 {
 	const char **new_branch = &opts->new_branch;
 	int argcount = 0;
@@ -1240,8 +1255,7 @@ static int parse_branchname_arg(int argc, const char **argv,
 
 		if (recover_with_dwim) {
 			const char *remote = parse_remote_branch(arg, rev,
-								 could_be_checkout_paths,
-								 dwim_remotes_matched);
+								 could_be_checkout_paths);
 			if (remote) {
 				*new_branch = arg;
 				arg = remote;
@@ -1505,7 +1519,6 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			 const char * const usagestr[])
 {
 	struct branch_info new_branch_info;
-	int dwim_remotes_matched = 0;
 	int parseopt_flags = 0;
 
 	memset(&new_branch_info, 0, sizeof(new_branch_info));
@@ -1613,8 +1626,7 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
 		int n = parse_branchname_arg(argc, argv, dwim_ok,
-					     &new_branch_info, opts, &rev,
-					     &dwim_remotes_matched);
+					     &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
@@ -1672,28 +1684,10 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 	}
 
 	UNLEAK(opts);
-	if (opts->patch_mode || opts->pathspec.nr) {
-		int ret = checkout_paths(opts, new_branch_info.name);
-		if (ret && dwim_remotes_matched > 1 &&
-		    advice_checkout_ambiguous_remote_branch_name)
-			advise(_("'%s' matched more than one remote tracking branch.\n"
-				 "We found %d remotes with a reference that matched. So we fell back\n"
-				 "on trying to resolve the argument as a path, but failed there too!\n"
-				 "\n"
-				 "If you meant to check out a remote tracking branch on, e.g. 'origin',\n"
-				 "you can do so by fully qualifying the name with the --track option:\n"
-				 "\n"
-				 "    git checkout --track origin/<name>\n"
-				 "\n"
-				 "If you'd like to always have checkouts of an ambiguous <name> prefer\n"
-				 "one remote, e.g. the 'origin' remote, consider setting\n"
-				 "checkout.defaultRemote=origin in your config."),
-			       argv[0],
-			       dwim_remotes_matched);
-		return ret;
-	} else {
+	if (opts->patch_mode || opts->pathspec.nr)
+		return checkout_paths(opts, new_branch_info.name);
+	else
 		return checkout_branch(opts, &new_branch_info);
-	}
 }
 
 int cmd_checkout(int argc, const char **argv, const char *prefix)
diff --git a/t/t2024-checkout-dwim.sh b/t/t2024-checkout-dwim.sh
index fa0718c730..707c88ceba 100755
--- a/t/t2024-checkout-dwim.sh
+++ b/t/t2024-checkout-dwim.sh
@@ -37,7 +37,9 @@ test_expect_success 'setup' '
 		git checkout -b foo &&
 		test_commit a_foo &&
 		git checkout -b bar &&
-		test_commit a_bar
+		test_commit a_bar &&
+		git checkout -b ambiguous_branch_and_file &&
+		test_commit a_ambiguous_branch_and_file
 	) &&
 	git init repo_b &&
 	(
@@ -46,7 +48,9 @@ test_expect_success 'setup' '
 		git checkout -b foo &&
 		test_commit b_foo &&
 		git checkout -b baz &&
-		test_commit b_baz
+		test_commit b_baz &&
+		git checkout -b ambiguous_branch_and_file &&
+		test_commit b_ambiguous_branch_and_file
 	) &&
 	git remote add repo_a repo_a &&
 	git remote add repo_b repo_b &&
@@ -75,6 +79,21 @@ test_expect_success 'checkout of branch from multiple remotes fails #1' '
 	test_branch master
 '
 
+test_expect_success 'when arg matches multiple remotes, do not fallback to interpreting as pathspec' '
+	git checkout -b t_ambiguous_branch_and_file &&
+	>ambiguous_branch_and_file &&
+	git add ambiguous_branch_and_file &&
+	git commit -m "ambiguous_branch_and_file" &&
+
+	test_when_finished "git checkout -- ambiguous_branch_and_file" &&
+	echo "file contents" >ambiguous_branch_and_file &&
+	cp ambiguous_branch_and_file expect &&
+
+	test_must_fail git checkout ambiguous_branch_and_file &&
+
+	test_cmp expect ambiguous_branch_and_file
+'
+
 test_expect_success 'checkout of branch from multiple remotes fails with advice' '
 	git checkout -B master &&
 	test_might_fail git branch -D foo &&

-- 
gitgitgadget
Previous: Alexandr Miloslavskiy via GitGitGadgetNext: Derrick Stolee
Message 3 of 13 in “checkout: die() on ambiguous tracking branches”
  1. 0/2 checkout: die() on ambiguous tracking branchesAlexandr Miloslavskiy via GitGitGadget, Nov 27, 2019
  2. 1/2 parse_branchname_arg(): extract part as new functionAlexandr Miloslavskiy via GitGitGadget, Nov 27, 2019
  3. 2/2 checkout: die() on ambiguous tracking branchesAlexandr Miloslavskiy via GitGitGadget, Nov 27, 2019
  4. Derrick StoleeNov 27, 2019
  5. Alexandr MiloslavskiyNov 27, 2019
  6. Ævar Arnfjörð BjarmasonNov 27, 2019
  7. Alexandr MiloslavskiyNov 27, 2019
  8. Alexandr MiloslavskiyDec 5, 2019
  9. 0/2 checkout: die() on ambiguous tracking branchesAlexandr Miloslavskiy via GitGitGadget, Nov 27, 2019
  10. 2/2 checkout: die() on ambiguous tracking branchesAlexandr Miloslavskiy via GitGitGadget, Nov 27, 2019
  11. 1/2 parse_branchname_arg(): extract part as new functionAlexandr Miloslavskiy via GitGitGadget, Nov 27, 2019
  12. Junio C HamanoDec 1, 2019
  13. Alexandr MiloslavskiyDec 1, 2019

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