[PATCH v4 0/3] t2400: Fix test failures when using grep 2.5

This patchset is in response to build failures on GGG's Cirrus CI freebsd_12 build jobs[1] and was prompted by a discussion thread [2]. These failures seem to be caused by the behavior outlined in [3].

Changes from v3:
  * Replace `[ ]` with ` ` in regex for `test_wt_add_orphan_hint()` [4][5].
  * Drop trailing `.*` from `invalid_ref_regex` [4][5].
  * Change `[a-z-]` to `[-a-z]` in `bad_combo_regex` to better portray
    intent [4][5].
  * Replace `\+` with `*` in `bad_combo_regex` as `\+` is not POSIX
    BRE and is a GNU extension [4][5].
  * Drop "without PCRE support" from commit message [4].
  * Reword commit message to reflect changes.

1. https://github.com/gitgitgadget/git/pull/1550/checks?check_run_id=14949695859
2. https://lore.kernel.org/git/CALnO6CDryTsguLshcQxx97ZxyY42Twu2hC2y1bLOsS-9zbqXMA@mail.gmail.com/
3. https://stackoverflow.com/questions/4233159/grep-regex-whitespace-behavior
4. https://lore.kernel.org/git/axnxvnmo6ekhhccppinji73ivlandwuqs44epmq4pdefm7ukiv@ejz7bee5xjli/
5. https://lore.kernel.org/git/xmqqiladw9h7.fsf@gitster.g/

Jacob Abel (3):
  t2400: drop no-op `--sq` from rev-parse call
  builtin/worktree.c: convert tab in advice to space
  t2400: rewrite regex to avoid unintentional PCRE

 builtin/worktree.c      |  4 ++--
 t/t2400-worktree-add.sh | 14 +++++++-------
 2 files changed, 9 insertions(+), 9 deletions(-)

Range-diff against v3:
1:  96c21c5bee = 1:  96c21c5bee t2400: drop no-op `--sq` from rev-parse call
2:  ebfba2d602 = 2:  ebfba2d602 builtin/worktree.c: convert tab in advice to space
3:  dee0c8f350 ! 3:  13f61cd15a t2400: rewrite regex to avoid unintentional PCRE
    @@ Commit message
         t2400: rewrite regex to avoid unintentional PCRE
     
         Replace all cases of `\s` with ` ` as it is not part of POSIX BRE or ERE
    -    and therefore not all versions of grep handle it without PCRE support.
    +    and therefore not all versions of grep handle it.
     
    -    For the same reason all cases of `\S` are replaced with `[^ ]`. It's not
    -    an exact replacement but it is close enough for this use case.
    +    For the same reason all cases of `\S` are replaced with `[^ ]`. It is
    +    not an exact replacement but it is close enough for this use case.
    +
    +    Also, do not write `\+` in BRE and expect it to mean 1 or more;
    +    it is a GNU extension that may not work everywhere.
    +
    +    Remove `.*` from the end of a pattern that is not right-anchored.
     
         Signed-off-by: Jacob Abel <jacobabel@nullpo.dev>
    +    Helped-by: Junio C Hamano <gitster@pobox.com>
     
      ## t/t2400-worktree-add.sh ##
     @@ t/t2400-worktree-add.sh: test_wt_add_orphan_hint () {
    @@ t/t2400-worktree-add.sh: test_wt_add_orphan_hint () {
      		if [ $use_branch -eq 1 ]
      		then
     -			grep -E "^hint:\s+git worktree add --orphan -b \S+ \S+\s*$" actual
    -+			grep -E "^hint:[ ]+git worktree add --orphan -b [^ ]+ [^ ]+$" actual
    ++			grep -E "^hint: +git worktree add --orphan -b [^ ]+ [^ ]+$" actual
      		else
     -			grep -E "^hint:\s+git worktree add --orphan \S+\s*$" actual
    -+			grep -E "^hint:[ ]+git worktree add --orphan [^ ]+$" actual
    ++			grep -E "^hint: +git worktree add --orphan [^ ]+$" actual
      		fi
      
      	'
    @@ t/t2400-worktree-add.sh: test_dwim_orphan () {
      	local fetch_error_text="fatal: No local or remote refs exist despite at least one remote" &&
      	local orphan_hint="hint: If you meant to create a worktree containing a new orphan branch" &&
     -	local invalid_ref_regex="^fatal: invalid reference:\s\+.*" &&
    -+	local invalid_ref_regex="^fatal: invalid reference: .*" &&
    - 	local bad_combo_regex="^fatal: '[a-z-]\+' and '[a-z-]\+' cannot be used together" &&
    +-	local bad_combo_regex="^fatal: '[a-z-]\+' and '[a-z-]\+' cannot be used together" &&
    ++	local invalid_ref_regex="^fatal: invalid reference: " &&
    ++	local bad_combo_regex="^fatal: '[-a-z]*' and '[-a-z]*' cannot be used together" &&
      
      	local git_ns="repo" &&
    + 	local dashc_args="-C $git_ns" &&
     @@ t/t2400-worktree-add.sh: test_dwim_orphan () {
      					headpath=$(git $dashc_args rev-parse --path-format=absolute --git-path HEAD) &&
      					headcontents=$(cat "$headpath") &&