Commit graph

15289 commits

Author SHA1 Message Date
Junio C Hamano 3526e67d91 Git 2.43.1
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-08 16:22:12 -08:00
Junio C Hamano 963eda258a Merge branch 'ib/rebase-reschedule-doc' into maint-2.43
Doc update.

* ib/rebase-reschedule-doc:
  rebase: clarify --reschedule-failed-exec default
2024-02-08 16:22:12 -08:00
Junio C Hamano d690c8e142 Merge branch 'ms/rebase-insnformat-doc-fix' into maint-2.43
Docfix.

* ms/rebase-insnformat-doc-fix:
  Documentation: fix statement about rebase.instructionFormat
2024-02-08 16:22:12 -08:00
Junio C Hamano 5a322a2d3d Merge branch 'js/contributor-docs-updates' into maint-2.43
Doc update.

* js/contributor-docs-updates:
  SubmittingPatches: hyphenate non-ASCII
  SubmittingPatches: clarify GitHub artifact format
  SubmittingPatches: clarify GitHub visual
  SubmittingPatches: provide tag naming advice
  SubmittingPatches: update extra tags list
  SubmittingPatches: discourage new trailers
  SubmittingPatches: drop ref to "What's in git.git"
  CodingGuidelines: write punctuation marks
  CodingGuidelines: move period inside parentheses
2024-02-08 16:22:11 -08:00
Junio C Hamano 3aea0dad70 Merge branch 'ml/doc-merge-updates' into maint-2.43
Doc update.

* ml/doc-merge-updates:
  Documentation/git-merge.txt: use backticks for command wrapping
  Documentation/git-merge.txt: fix reference to synopsis
2024-02-08 16:22:10 -08:00
Junio C Hamano 974c9369aa Merge branch 'jc/orphan-unborn' into maint-2.43
Doc updates to clarify what an "unborn branch" means.

* jc/orphan-unborn:
  orphan/unborn: fix use of 'orphan' in end-user facing messages
  orphan/unborn: add to the glossary and use them consistently
2024-02-08 16:22:10 -08:00
Junio C Hamano a1121a79d9 Merge branch 'jc/doc-misspelt-refs-fix' into maint-2.43
Doc update.

* jc/doc-misspelt-refs-fix:
  doc: format.notes specify a ref under refs/notes/ hierarchy
2024-02-08 16:22:08 -08:00
Junio C Hamano 79f79e58a4 Merge branch 'jc/doc-most-refs-are-not-that-special' into maint-2.43
Doc updates.

* jc/doc-most-refs-are-not-that-special:
  docs: MERGE_AUTOSTASH is not that special
  docs: AUTO_MERGE is not that special
  refs.h: HEAD is not that special
  git-bisect.txt: BISECT_HEAD is not that special
  git.txt: HEAD is not that special
2024-02-08 16:22:08 -08:00
Junio C Hamano 7b95c64408 Merge branch 'es/add-doc-list-short-form-of-all-in-synopsis' into maint-2.43
Doc update.

* es/add-doc-list-short-form-of-all-in-synopsis:
  git-add.txt: add missing short option -A to synopsis
2024-02-08 16:22:08 -08:00
Junio C Hamano 1dbc46997a Merge branch 'mk/doc-gitfile-more' into maint-2.43
Doc update.

* mk/doc-gitfile-more:
  doc: make the gitfile syntax easier to discover
2024-02-08 16:22:06 -08:00
Junio C Hamano 3c2ee131f8 Merge branch 'cp/git-flush-is-an-env-bool' into maint-2.43
Unlike other environment variables that took the usual
true/false/yes/no as well as 0/1, GIT_FLUSH only understood 0/1,
which has been corrected.

* cp/git-flush-is-an-env-bool:
  write-or-die: make GIT_FLUSH a Boolean environment variable
2024-02-08 16:22:04 -08:00
Junio C Hamano efbae0583b Merge branch 'js/update-urls-in-doc-and-comment' into maint-2.43
Stale URLs have been updated to their current counterparts (or
archive.org) and HTTP links are replaced with working HTTPS links.

* js/update-urls-in-doc-and-comment:
  doc: refer to internet archive
  doc: update links for andre-simon.de
  doc: switch links to https
  doc: update links to current pages
2024-02-08 16:22:01 -08:00
Junio C Hamano 50b8f513a2 Merge branch 'ps/commit-graph-less-paranoid' into maint-2.43
Earlier we stopped relying on commit-graph that (still) records
information about commits that are lost from the object store,
which has negative performance implications.  The default has been
flipped to disable this pessimization.

* ps/commit-graph-less-paranoid:
  commit-graph: disable GIT_COMMIT_GRAPH_PARANOIA by default
2024-02-08 16:22:01 -08:00
Junio C Hamano f8e2ad965a Merge branch 'tz/send-email-negatable-options' into maint-2.43
Newer versions of Getopt::Long started giving warnings against our
(ab)use of it in "git send-email".  Bump the minimum version
requirement for Perl to 5.8.1 (from September 2002) to allow
simplifying our implementation.

* tz/send-email-negatable-options:
  send-email: avoid duplicate specification warnings
  perl: bump the required Perl version to 5.8.1 from 5.8.0
2024-02-08 16:22:01 -08:00
Illia Bobyr 25aec06326 rebase: clarify --reschedule-failed-exec default
Documentation should mention the default behavior.

It is better to explain the persistent nature of the
--reschedule-failed-exec flag from the user standpoint, rather than from
the implementation standpoint.

Signed-off-by: Illia Bobyr <illia.bobyr@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-05 09:41:25 -08:00
Chandra Pratap 556e68032f write-or-die: make GIT_FLUSH a Boolean environment variable
Among Git's environment variables, the ones marked as "Boolean"
accept values in a way similar to Boolean configuration variables,
i.e. values like 'yes', 'on', 'true' and positive numbers are
taken as "on" and values like 'no', 'off', 'false' are taken as
"off".

GIT_FLUSH can be used to force Git to use non-buffered I/O when
writing to stdout. It can only accept two values, '1' which causes
Git to flush more often and '0' which makes all output buffered.
Make GIT_FLUSH accept more values besides '0' and '1' by turning it
into a Boolean environment variable, modifying the required logic.
Update the related documentation.

Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-04 10:32:21 -08:00
Maarten van der Schrieck 9cd30af991 Documentation: fix statement about rebase.instructionFormat
Since commit 62db5247 (rebase -i: generate the script via
rebase--helper, 2017-07-14), the short hash is given in
rebase-todo. Specifying rebase.instructionFormat does not alter this
behavior, contrary to what the documentation implies.

Signed-off-by: Maarten van der Schrieck <maarten@thingsconnected.nl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-01-03 11:21:15 -08:00
Josh Soref 291873e5d6 SubmittingPatches: hyphenate non-ASCII
Git documentation does this with the exception of ancient release notes.

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:24 -08:00
Josh Soref 7818951623 SubmittingPatches: clarify GitHub artifact format
GitHub wraps artifacts generated by workflows in a .zip file.

Internally, workflows can package anything they like in them.

A recently generated failure artifact had the form:

windows-artifacts.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
 76001695  12-19-2023 01:35   artifacts.tar.gz
 11005650  12-19-2023 01:35   tracked.tar.gz
---------                     -------
 87007345                     2 files

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:24 -08:00
Josh Soref 0771a3b55c SubmittingPatches: clarify GitHub visual
GitHub has two general forms for its states, sometimes they're a simple
colored object (e.g. green check or red x), and sometimes there's also a
colored container (e.g. green box or red circle) which contains that
object (e.g. check or x).

That's a lot of words to try to describe things, but in general, the key
for a failure is that it's recognized as an `x` and that it's associated
with the color red -- the color of course is problematic for people who
are red-green color-blind, but that's why they are paired with distinct
shapes.

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:24 -08:00
Josh Soref 08e2e6f8d2 SubmittingPatches: provide tag naming advice
Current statistics show a strong preference to only capitalize the first
letter in a hyphenated tag, but that some guidance would be helpful:

git log |
  perl -ne 'next unless /^\s+(?:Signed-[oO]ff|Acked)-[bB]y:/;
    s/^\s+//;s/:.*/:/;print'|
  sort|uniq -c|sort -n
   2 Signed-off-By:
   4 Signed-Off-by:
  22 Acked-By:
  47 Signed-Off-By:
2202 Acked-by:
95315 Signed-off-by:

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:23 -08:00
Josh Soref c771ef6f77 SubmittingPatches: update extra tags list
Add items with at least 100 uses in the past three years:
- Co-authored-by
- Helped-by
- Mentored-by
- Suggested-by

git log --since=3.years|
  perl -ne 'next unless /^\s+[A-Z][a-z]+-\S+:/;s/^\s+//;s/:.*/:/;print'|
  sort|uniq -c|sort -n|grep '[0-9][0-9] '
  14 Based-on-patch-by:
  14 Original-patch-by:
  17 Tested-by:
 100 Suggested-by:
 121 Co-authored-by:
 163 Mentored-by:
 274 Reported-by:
 290 Acked-by:
 450 Helped-by:
 602 Reviewed-by:
14111 Signed-off-by:

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:23 -08:00
Josh Soref ac9fff2bf1 SubmittingPatches: discourage new trailers
There seems to be consensus amongst the core Git community on a working
set of common trailers, and there are non-trivial costs to people
inventing new trailers (research to discover what they mean/how they
differ from existing trailers) such that inventing new ones is generally
unwarranted and not something to be recommended to new contributors.

Suggested-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:23 -08:00
Josh Soref 127106294a SubmittingPatches: drop ref to "What's in git.git"
"What's in git.git" was last seen in 2010:
  https://lore.kernel.org/git/?q=%22what%27s+in+git.git%22
  https://lore.kernel.org/git/7vaavikg72.fsf@alter.siamese.dyndns.org/

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:23 -08:00
Josh Soref e6397c5cc8 CodingGuidelines: write punctuation marks
- Match style in Release Notes

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:23 -08:00
Josh Soref 2d194548cb CodingGuidelines: move period inside parentheses
The contents within parenthesis should be omittable without resulting
in broken text.

Eliding the parenthesis left a period to end a run without any content.

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-27 21:33:23 -08:00
Michael Lohmann 63956c553d Documentation/git-merge.txt: use backticks for command wrapping
As René found in the guidance from CodingGuidelines:

   Literal examples (e.g. use of command-line options, command names,
   branch names, URLs, pathnames (files and directories), configuration
   and environment variables) must be typeset in monospace (i.e. wrapped
   with backticks)

So all instances of single and double quotes for wraping said examples
were replaced with simple backticks.

Suggested-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Michael Lohmann <mi.al.lohmann@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-20 13:40:01 -08:00
Michael Lohmann dc18ead555 Documentation/git-merge.txt: fix reference to synopsis
437591a9d7 combined the synopsis of "The second syntax" (meaning `git
merge --abort`) and "The third syntax" (for `git merge --continue`) into
this single line:

       git merge (--continue | --abort | --quit)

but it was still referred to when describing the preconditions that have
to be fulfilled to run the respective actions. In other words:
References by number are no longer valid after a merge of some of the
synopses.

Also the previous version of the documentation did not acknowledge that
`--no-commit` would result in the precondition being fulfilled (thanks
to Elijah Newren and Junio C Hamano for pointing that out).

This change also groups `--abort` and `--continue` together when
explaining the prerequisites in order to avoid duplication.

Helped-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Michael Lohmann <mi.al.lohmann@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-20 13:39:56 -08:00
Junio C Hamano 6d6f1cd7ee doc: format.notes specify a ref under refs/notes/ hierarchy
There is no 'ref/notes/' hierarchy.  '[format] notes = foo' uses notes
that are found in 'refs/notes/foo'.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-18 11:30:46 -08:00
Junio C Hamano bc62d27d5c docs: MERGE_AUTOSTASH is not that special
A handful of manual pages called MERGE_AUTOSTASH a "special ref",
but there is nothing special about it.  It merely is yet another
pseudoref.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-15 14:08:28 -08:00
Junio C Hamano dada38646a docs: AUTO_MERGE is not that special
A handful of manual pages called AUTO_MERGE a "special ref", but
there is nothing special about it.  It merely is yet another
pseudoref.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-15 14:08:28 -08:00
Junio C Hamano 2047b2c28c git-bisect.txt: BISECT_HEAD is not that special
The description of "git bisect --no-checkout" called BISECT_HEAD a
"special ref", but there is nothing special about it.  It merely is
yet another pseudoref.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-15 14:08:28 -08:00
Junio C Hamano d9a4bb3385 git.txt: HEAD is not that special
The introductory text in "git help git" that describes HEAD called
it "a special ref".  It is special compared to the more regular refs
like refs/heads/master and refs/tags/v1.0.0, but not that special,
unlike truly special ones like FETCH_HEAD.

Rewrite a few sentences to also introduce the distinction between a
regular ref that contain the object name and a symbolic ref that
contain the name of another ref.  Update the description of HEAD
that point at the current branch to use the more correct term, a
"symbolic ref".

This was found as part of auditing the documentation and in-code
comments for uses of "special ref" that refer merely a "pseudo ref".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-15 14:08:21 -08:00
Eric Sunshine 68fcebfb1a git-add.txt: add missing short option -A to synopsis
With one exception, the synopsis for `git add` consistently lists the
short counterpart alongside the long-form of each option (for instance,
"[--edit | -e]"). The exception is that -A is not mentioned alongside
--all. Fix this inconsistency

Reported-by: Benjamin Lehmann <ben.lehmann@gmail.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-15 13:01:51 -08:00
Marcel Krause e4299d26d4 doc: make the gitfile syntax easier to discover
Signed-off-by: Marcel Krause <mk+copyleft@pimpmybyte.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-03 10:54:51 +09:00
Patrick Steinhardt b1df3b3867 commit-graph: disable GIT_COMMIT_GRAPH_PARANOIA by default
In 7a5d604443 (commit: detect commits that exist in commit-graph but not
in the ODB, 2023-10-31), we have introduced a new object existence check
into `repo_parse_commit_internal()` so that we do not parse commits via
the commit-graph that don't have a corresponding object in the object
database. This new check of course comes with a performance penalty,
which the commit put at around 30% for `git rev-list --topo-order`. But
there are in fact scenarios where the performance regression is even
higher. The following benchmark against linux.git with a fully-build
commit-graph:

  Benchmark 1: git.v2.42.1 rev-list --count HEAD
    Time (mean ± σ):     658.0 ms ±   5.2 ms    [User: 613.5 ms, System: 44.4 ms]
    Range (min … max):   650.2 ms … 666.0 ms    10 runs

  Benchmark 2: git.v2.43.0-rc1 rev-list --count HEAD
    Time (mean ± σ):      1.333 s ±  0.019 s    [User: 1.263 s, System: 0.069 s]
    Range (min … max):    1.302 s …  1.361 s    10 runs

  Summary
    git.v2.42.1 rev-list --count HEAD ran
      2.03 ± 0.03 times faster than git.v2.43.0-rc1 rev-list --count HEAD

While it's a noble goal to ensure that results are the same regardless
of whether or not we have a potentially stale commit-graph, taking twice
as much time is a tough sell. Furthermore, we can generally assume that
the commit-graph will be updated by git-gc(1) or git-maintenance(1) as
required so that the case where the commit-graph is stale should not at
all be common.

With that in mind, default-disable GIT_COMMIT_GRAPH_PARANOIA and restore
the behaviour and thus performance previous to the mentioned commit. In
order to not be inconsistent, also disable this behaviour by default in
`lookup_commit_in_graph()`, where the object existence check has been
introduced right at its inception via f559d6d45e (revision: avoid
hitting packfiles when commits are in commit-graph, 2021-08-09).

This results in another speedup in commands that end up calling this
function, even though it's less pronounced compared to the above
benchmark. The following has been executed in linux.git with ~1.2
million references:

  Benchmark 1: GIT_COMMIT_GRAPH_PARANOIA=true git rev-list --all --no-walk=unsorted
    Time (mean ± σ):      2.947 s ±  0.003 s    [User: 2.412 s, System: 0.534 s]
    Range (min … max):    2.943 s …  2.949 s    3 runs

  Benchmark 2: GIT_COMMIT_GRAPH_PARANOIA=false git rev-list --all --no-walk=unsorted
    Time (mean ± σ):      2.724 s ±  0.030 s    [User: 2.207 s, System: 0.514 s]
    Range (min … max):    2.704 s …  2.759 s    3 runs

  Summary
    GIT_COMMIT_GRAPH_PARANOIA=false git rev-list --all --no-walk=unsorted ran
      1.08 ± 0.01 times faster than GIT_COMMIT_GRAPH_PARANOIA=true git rev-list --all --no-walk=unsorted

So whereas 7a5d604443 initially introduced the logic to start doing an
object existence check in `repo_parse_commit_internal()` by default, the
updated logic will now instead cause `lookup_commit_in_graph()` to stop
doing the check by default. This behaviour continues to be tweakable by
the user via the GIT_COMMIT_GRAPH_PARANOIA environment variable.

Note that this requires us to amend some tests to manually turn on the
paranoid checks again. This is because we cause repository corruption by
manually deleting objects which are part of the commit graph already.
These circumstances shouldn't usually happen in repositories.

Reported-by: Jeff King <peff@peff.net>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-26 10:10:00 +09:00
Josh Soref 28a0c65f5d doc: update links for andre-simon.de
Beyond the fact that it's somewhat traditional to respect sites'
self-identification, it's helpful for links to point to the things
that people expect them to reference. Here that means linking to
specific pages instead of a domain.

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-26 10:07:05 +09:00
Josh Soref d05b08cd52 doc: switch links to https
These sites offer https versions of their content.
Using the https versions provides some protection for users.

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-26 10:07:05 +09:00
Josh Soref 65175d9ea2 doc: update links to current pages
It's somewhat traditional to respect sites' self-identification.

Signed-off-by: Josh Soref <jsoref@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-26 10:07:05 +09:00
Junio C Hamano 49dc156376 orphan/unborn: add to the glossary and use them consistently
To orphan is a verb that denotes the act of getting on an unborn
branch, and a few references to "orphan branch" in our documentation
are misuses of the word.  They caused end-user confusion, which was
made even worse because we did not have the term defined in the
glossary document.  Add entries for "unborn" branch and "orphan"
operation to the glossary, and adjust existing documentation
accordingly.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-24 12:11:23 +09:00
Junio C Hamano 564d0252ca Git 2.43
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-20 10:28:15 +09:00
Junio C Hamano d003a26cca Merge branch 'vd/glossary-dereference-peel'
"To dereference" and "to peel" were sometimes used in in-code
comments and documentation but without description in the glossary.

* vd/glossary-dereference-peel:
  glossary: add definitions for dereference & peel
2023-11-20 09:57:23 +09:00
Todd Zullinger d13a73e383 perl: bump the required Perl version to 5.8.1 from 5.8.0
The following commit will make use of a Getopt::Long feature which is
only present in Perl >= 5.8.1.  Document that as the minimum version we
support.

Many of our Perl scripts will continue to run with 5.8.0 but this change
allows us to adjust them as needed without breaking any promises to our
users.

The Perl requirement was last changed in d48b284183 (perl: bump the
required Perl version to 5.8 from 5.6.[21], 2010-09-24).  At that time,
5.8.0 was 8 years old.  It is now over 21 years old.

Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-17 07:26:32 +09:00
Victoria Dye 893dce2ffb glossary: add definitions for dereference & peel
Add 'gitglossary' definitions for "dereference" (as it used for both symrefs
and objects) and "peel". These terms are used in options and documentation
throughout Git, but they are not clearly defined anywhere and the behavior
they refer to depends heavily on context. Provide explicit definitions to
clarify existing documentation to users and help contributors to use the
most appropriate terminology possible in their additions to Git.

Update other definitions in the glossary that use the term "dereference" to
link to 'def_dereference'.

Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-14 09:49:33 +09:00
Elijah Newren e0939bec27 RelNotes: minor wording fixes in 2.43.0 release notes
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-12 09:59:28 +09:00
Junio C Hamano dadef801b3 Git 2.43-rc1
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-08 15:04:42 +09:00
Junio C Hamano 98009afd24 Prepare for -rc1
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-11-08 11:04:03 +09:00
Junio C Hamano 259e30d2bb Merge branch 'bc/merge-file-object-input'
"git merge-file" learns a mode to read three contents to be merged
from blob objects.

* bc/merge-file-object-input:
  merge-file: add an option to process object IDs
  git-merge-file doc: drop "-file" from argument placeholders
2023-11-08 11:04:01 +09:00
Junio C Hamano ed14fa1c2a Merge branch 'tb/format-pack-doc-update'
Doc update.

* tb/format-pack-doc-update:
  Documentation/gitformat-pack.txt: fix incorrect MIDX documentation
  Documentation/gitformat-pack.txt: fix typo
2023-11-08 11:04:00 +09:00
Junio C Hamano d8972a5abd Merge branch 'ps/show-ref'
Teach "git show-ref" a mode to check the existence of a ref.

* ps/show-ref:
  t: use git-show-ref(1) to check for ref existence
  builtin/show-ref: add new mode to check for reference existence
  builtin/show-ref: explicitly spell out different modes in synopsis
  builtin/show-ref: ensure mutual exclusiveness of subcommands
  builtin/show-ref: refactor options for patterns subcommand
  builtin/show-ref: stop using global vars for `show_one()`
  builtin/show-ref: stop using global variable to count matches
  builtin/show-ref: refactor `--exclude-existing` options
  builtin/show-ref: fix dead code when passing patterns
  builtin/show-ref: fix leaking string buffer
  builtin/show-ref: split up different subcommands
  builtin/show-ref: convert pattern to a local variable
2023-11-08 11:04:00 +09:00