branch/push: suggest intended form when remote/branch slip given

When the repository or upstream argument is a slip like "origin/main" or "origin main", suggest the intended "git push origin main" or "git branch --set-upstream-to=origin/main" form instead of failing with an unrelated error.

Changes in v3:

* Reworded the branch commit message to also show the second confusing error (the requested upstream branch 'origin' does not exist) for when the operated-on branch does exist.
* Converted the new t5529 tests from bare grep/! grep to test_grep to fix the test-lint failures.
* Added a brief call-site comment explaining the up-front advice_enabled() gate (skips the lookups when the hint is off, while advise_if_enabled() still prints the disable-message footer).

Changes in v2:

* Rewrote both commit messages to lead with the intended command, the easy slip, and the resulting error, instead of the terse original.
* Gated each suggestion on advice_enabled() up front, so a user who silenced the hint pays no remote/ref lookups and falls through to the original error. Extracted the detection logic into helpers (die_if_repo_looks_like_ref, die_if_upstream_looks_like_remote) so each call site reads as a single guarded line.

Harald Nordgren (2):
branch: suggest <remote>/<branch> on upstream slip
push: suggest <remote> <branch> for a slash slip

 Documentation/config/advice.adoc |  5 +++++
 advice.c                         |  1 +
 advice.h                         |  1 +
 builtin/branch.c                 | 32 +++++++++++++++++++++++++++
 builtin/push.c                   | 37 ++++++++++++++++++++++++++++++-
 t/t3200-branch.sh                | 38 ++++++++++++++++++++++++++++++++
 t/t5529-push-errors.sh           | 31 ++++++++++++++++++++++++++
 7 files changed, 144 insertions(+), 1 deletion(-)

base-commit: ab776a62a78576513ee121424adb19597fbb7613
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2331%2FHaraldNordgren%2Fsuggest-remote-branch-slips-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2331/HaraldNordgren/suggest-remote-branch-slips-v3
Pull-Request: https://github.com/git/git/pull/2331

Range-diff vs v2:

1: 11bcecebf4 ! 1: 9883c28482 branch: suggest <remote>/<branch> on upstream slip
@@ Commit message

fatal: branch 'main' does not exist

- pointing at a branch the user never meant to name.
+ pointing at a branch the user never meant to name. When 'main' does
+ exist, it instead dies with:
+
+ fatal: the requested upstream branch 'origin' does not exist
+
+ leaving the user equally puzzled.

When the operated-on branch is missing and '<remote>/<branch>' names a real remote-tracking ref, suggest the intended form:
@@ builtin/branch.c: int cmd_branch(int argc,
if (!refs_ref_exists(get_main_ref_store(the_repository), branch->refname)) {
if (!argc || branch_checked_out(branch->refname))
die(_("no commit on branch '%s' yet"), branch->name);
++ /*
++ * Check the advice up front to avoid the ref
++ * lookups when the hint is off. The helper still
++ * calls advise_if_enabled() so the hint carries the
++ * standard "disable this message" instructions.
++ */
+ if (argc == 1 &&
+ advice_enabled(ADVICE_SET_UPSTREAM_FAILURE))
+ die_if_upstream_looks_like_remote(new_upstream, argv[0]);
2: 49de5a925d ! 2: dbe4dbc346 push: suggest <remote> <branch> for a slash slip

     @@ builtin/push.c: int cmd_push(int argc,
       		if (!add_remote_or_group(repo, &remote_group)) {
      +			struct remote *r;
      +
     ++			/*
     ++			 * Check the advice up front to avoid the remote
     ++			 * lookup when the hint is off. The helper still
     ++			 * calls advise_if_enabled() so the hint carries the
     ++			 * standard "disable this message" instructions.
     ++			 */
      +			if (advice_enabled(ADVICE_PUSH_REPO_LOOKS_LIKE_REF))
      +				die_if_repo_looks_like_ref(repo);
      +
     @@ t/t5529-push-errors.sh: test_expect_success 'detect empty remote with targeted r
       
      +test_expect_success 'suggest <remote> <branch> for a <remote>/<branch> slip' '
      +	test_must_fail git push origin/main 2>stderr &&
     -+	grep "${SQ}origin/main${SQ} is not a valid push target" stderr &&
     -+	grep "hint: Did you mean to use: git push origin main?" stderr &&
     ++	test_grep "${SQ}origin/main${SQ} is not a valid push target" stderr &&
     ++	test_grep "hint: Did you mean to use: git push origin main?" stderr &&
      +	test_must_fail git -c advice.pushRepoLooksLikeRef=false push origin/main 2>stderr &&
     -+	! grep "Did you mean" stderr
     ++	test_grep ! "Did you mean" stderr
      +'
      +
      +test_expect_success 'suggest <remote> <branch> when the branch has slashes' '
      +	test_must_fail git push origin/feature/x 2>stderr &&
     -+	grep "hint: Did you mean to use: git push origin feature/x?" stderr
     ++	test_grep "hint: Did you mean to use: git push origin feature/x?" stderr
      +'
      +
      +test_expect_success 'no suggestion when prefix is not a configured remote' '
      +	test_must_fail git push not-a-remote/main 2>stderr &&
     -+	! grep "Did you mean" stderr
     ++	test_grep ! "Did you mean" stderr
      +'
      +
      +test_expect_success 'no suggestion for a trailing slash with no branch' '
      +	test_must_fail git push origin/ 2>stderr &&
     -+	! grep "Did you mean" stderr
     ++	test_grep ! "Did you mean" stderr
      +'
      +
      +test_expect_success 'no suggestion when the argument is an existing path' '
      +	test_when_finished "rm -rf origin" &&
      +	git init --bare origin/main &&
      +	git push origin/main HEAD:refs/heads/pushed 2>stderr &&
     -+	! grep "Did you mean" stderr &&
     ++	test_grep ! "Did you mean" stderr &&
      +	git -C origin/main rev-parse --verify refs/heads/pushed
      +'
      +

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