[GSoC][RFC PATCH v2 0/2] Add refs list subcommand

[Meet Soni <meetsoni3017@gmail.com>]

Hello everyone,

This is the second version of the patch series that introduces the `git
refs list` subcommand as a modern alternative to `git for-each-ref`.

Thank you to everyone who provided valuable feedback on the first
version. This new version incorporates the suggestions, improving both
the code's implementation and the documentation's structure.

Changes in v2:
  - Refactored the implementation of `refs list`. Instead of duplicating
    the logic from `for-each-ref`, it is now a thin wrapper that
    calls the original command. This avoids code duplication while
    maintaining identical behavior.

  - Refactored the documentation by moving the common command options
    shared by `refs list` and `for-each-ref` into a new standalone
    file (`ref-list-options.adoc`).

  - Both man pages now use the AsciiDoc `include::` macro to embed these
    shared options, ensuring documentation stays consistent.

---

(v1 cover-letter text)

This patch series introduces `git refs list` as a modern replacement for
`git for-each-ref`, as part of an effort to consolidate ref-related
functionality under a unified `git refs` command.

Git's ref-related operations are currently handled by several distinct
commands, such as `git show-ref`, `git for-each-ref`, `git update-ref`,
`git pack-refs`, etc. This distribution has a few practical drawbacks:

- Users need to rely on multiple commands for related tasks involving
  refs.

- The commands may differ slightly in behavior and option syntax,
  leading to inconsistency.

We propose a long-term consolidation effort to bring ref-related
subcommands under the umbrella of a single command: `git refs`.

The implementation of `git refs list` is functionally identical to `git
for-each-ref`. It reuses the same internal logic (cmd_for_each_ref) to
ensure complete backward compatibility. The purpose of this patch is not
to introduce new behavior but to provide an alternate entry point under
the consolidated `git refs` namespace.

The motivation behind this change is twofold:

- Consolidation: Centralizing ref-related operations makes them easier
  to discover, use, and maintain.

- Evolution: While the initial goal is parity with existing commands,
  this consolidation allows for careful reconsideration of which
  features are essential. Over time, we can:

  - Remove legacy or obscure options that are no longer needed.
  - Add improvements that wouldn't make sense to bolt onto legacy
    commands.
  - Offering a more consistent and user-friendly surface.

To verify backward compatibility, this patch also includes a test
`t/t1461-refs-list.sh`, which runs the full `t6300-for-each-ref.sh` test
using `git refs list`. The test uses ${GIT_REFS_LIST_CMD:-for-each-ref}
to allow substitution without duplicating tests.

This patch is deliberately conservative: it introduces no behavioral
changes and leaves `for-each-ref` untouched. The goal is to lay
groundwork and demonstrate viability of ref consolidation within `git
refs`.

Going forward, I'd like to initiate a discussion on what the ideal
surface of `git refs list` should look like. Which options and features
from `for-each-ref` should be carried over? Are there any that are
obsolete or overly niche? What improvements might be worth considering
now that we have a new, consolidated interface?

Feedback on this, especially from those who rely on `for-each-ref` in
scripts or tooling would be very helpful.

Meet Soni (2):
  builtin/refs: add list subcommand
  t: add test for git refs list subcommand

 Documentation/git-for-each-ref.adoc  |  80 +------
 Documentation/git-refs.adoc          |  16 ++
 Documentation/refs-list-options.adoc |  80 +++++++
 builtin/for-each-ref.c               |  24 +-
 builtin/refs.c                       |  35 +++
 t/meson.build                        |   1 +
 t/t1461-refs-list.sh                 |   8 +
 t/t6300-for-each-ref.sh              | 333 ++++++++++++++-------------
 8 files changed, 331 insertions(+), 246 deletions(-)
 create mode 100644 Documentation/refs-list-options.adoc
 create mode 100755 t/t1461-refs-list.sh

Range-diff against v1:
1:  e7b19c71eb ! 1:  b2d3026520 builtin/refs: add list subcommand
    @@ Commit message
         instead of duplicating its logic. Forward all arguments to the existing
         function to ensure behavior is identical.
     
    -    This prevents code duplication and allows `refs list` to benefit from
    -    any future fixes to the underlying `for-each-ref` machinery.
    +    Add documentation for the new command. To keep the documentation DRY and
    +    consistent with `git-for-each-ref(1)`, refactor the shared command
    +    options into a standalone file. Use the AsciiDoc `include::` macro to
    +    embed these options in both man pages.
    +
    +    This prevents duplication in both code and documentation, ensuring that
    +    `refs list` benefits from any future fixes to the underlying
    +    `for-each-ref` machinery and its shared documentation.
     
         Mentored-by: Patrick Steinhardt <ps@pks.im>
         Mentored-by: shejialuo <shejialuo@gmail.com>
         Mentored-by: Karthik Nayak <karthik.188@gmail.com>
         Signed-off-by: Meet Soni <meetsoni3017@gmail.com>
     
    + ## Documentation/git-for-each-ref.adoc ##
    +@@ Documentation/git-for-each-ref.adoc: host language allowing their direct evaluation in that language.
    + 
    + OPTIONS
    + -------
    +-<pattern>...::
    +-	If one or more patterns are given, only refs are shown that
    +-	match against at least one pattern, either using fnmatch(3) or
    +-	literally, in the latter case matching completely or from the
    +-	beginning up to a slash.
    +-
    +---stdin::
    +-	If `--stdin` is supplied, then the list of patterns is read from
    +-	standard input instead of from the argument list.
    +-
    +---count=<count>::
    +-	By default the command shows all refs that match
    +-	`<pattern>`.  This option makes it stop after showing
    +-	that many refs.
    +-
    +---sort=<key>::
    +-	A field name to sort on.  Prefix `-` to sort in
    +-	descending order of the value.  When unspecified,
    +-	`refname` is used.  You may use the --sort=<key> option
    +-	multiple times, in which case the last key becomes the primary
    +-	key.
    +-
    +---format=<format>::
    +-	A string that interpolates `%(fieldname)` from a ref being shown and
    +-	the object it points at. In addition, the string literal `%%`
    +-	renders as `%` and `%xx` - where `xx` are hex digits - renders as
    +-	the character with hex code `xx`. For example, `%00` interpolates to
    +-	`\0` (NUL), `%09` to `\t` (TAB), and `%0a` to `\n` (LF).
    +-+
    +-When unspecified, `<format>` defaults to `%(objectname) SPC %(objecttype)
    +-TAB %(refname)`.
    +-
    +---color[=<when>]::
    +-	Respect any colors specified in the `--format` option. The
    +-	`<when>` field must be one of `always`, `never`, or `auto` (if
    +-	`<when>` is absent, behave as if `always` was given).
    +-
    +---shell::
    +---perl::
    +---python::
    +---tcl::
    +-	If given, strings that substitute `%(fieldname)`
    +-	placeholders are quoted as string literals suitable for
    +-	the specified host language.  This is meant to produce
    +-	a scriptlet that can directly be `eval`ed.
    +-
    +---points-at=<object>::
    +-	Only list refs which points at the given object.
    +-
    +---merged[=<object>]::
    +-	Only list refs whose tips are reachable from the
    +-	specified commit (HEAD if not specified).
    +-
    +---no-merged[=<object>]::
    +-	Only list refs whose tips are not reachable from the
    +-	specified commit (HEAD if not specified).
    +-
    +---contains[=<object>]::
    +-	Only list refs which contain the specified commit (HEAD if not
    +-	specified).
    +-
    +---no-contains[=<object>]::
    +-	Only list refs which don't contain the specified commit (HEAD
    +-	if not specified).
    +-
    +---ignore-case::
    +-	Sorting and filtering refs are case insensitive.
    +-
    +---omit-empty::
    +-	Do not print a newline after formatted refs where the format expands
    +-	to the empty string.
    +-
    +---exclude=<pattern>::
    +-	If one or more patterns are given, only refs which do not match
    +-	any excluded pattern(s) are shown. Matching is done using the
    +-	same rules as `<pattern>` above.
    +-
    +---include-root-refs::
    +-	List root refs (HEAD and pseudorefs) apart from regular refs.
    ++include::refs-list-options.adoc[]
    + 
    + FIELD NAMES
    + -----------
    +
      ## Documentation/git-refs.adoc ##
     @@ Documentation/git-refs.adoc: SYNOPSIS
      [synopsis]
    @@ Documentation/git-refs.adoc: migrate::
      	Verify reference database consistency.
      
     +list::
    -+	List references in the repository with support for filtering, formatting,
    -+	and sorting. This subcommand uses the same core logic as
    -+	linkgit:git-for-each-ref[1] and offers equivalent functionality.
    ++	List references in the repository with support for filtering,
    ++	formatting, and sorting. This subcommand is an alias for
    ++	linkgit:git-for-each-ref[1] and offers identical functionality.
     +
      OPTIONS
      -------
    @@ Documentation/git-refs.adoc: The following options are specific to 'git refs ver
      
     +The following options are specific to 'git refs list':
     +
    ++include::refs-list-options.adoc[]
    ++
    + KNOWN LIMITATIONS
    + -----------------
    + 
    +
    + ## Documentation/refs-list-options.adoc (new) ##
    +@@
    ++// Shared options for for-each-ref and refs list
     +<pattern>...::
     +	If one or more patterns are given, only refs are shown that
     +	match against at least one pattern, either using fnmatch(3) or
    @@ Documentation/git-refs.adoc: The following options are specific to 'git refs ver
     +
     +--include-root-refs::
     +	List root refs (HEAD and pseudorefs) apart from regular refs.
    -+
    -+
    - KNOWN LIMITATIONS
    - -----------------
    - 
     
      ## builtin/for-each-ref.c ##
     @@ builtin/for-each-ref.c: static char const * const for_each_ref_usage[] = {
2:  8ce521880c = 2:  2d6534841f t: add test for git refs list subcommand
-- 
2.34.1