builtin/refs: add 'exists' subcommand

As part of the ongoing effort to consolidate reference handling,
introduce a new `exists` subcommand. This command provides the same
functionality and exit-code behavior as `git show-ref --exists`, serving
as its modern replacement.

The logic for `show-ref --exists` is minimal. Rather than creating a
shared helper function which would be overkill for ~20 lines of code,
its implementation is intentionally duplicated here. This contrasts with
`git refs list`, where sharing the larger implementation of
`for-each-ref` was necessary.

Documentation for the new subcommand is also added to the `git-refs(1)`
man page.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: shejialuo <shejialuo@gmail.com>
Signed-off-by: Meet Soni <meetsoni3017@gmail.com>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-refs.adoc b/Documentation/git-refs.adoc
index e608980711814ae4c7b186efdb4eb5a25cb8ae0a..5d2032b318a224d3b5cea82d203373be367168f7 100644 (file)
--- a/Documentation/git-refs.adoc
+++ b/Documentation/git-refs.adoc
@@ -18,6 +18,7 @@ git refs list [--count=<count>] [--shell|--perl|--python|--tcl]
                   [--contains[=<object>]] [--no-contains[=<object>]]
                   [(--exclude=<pattern>)...] [--start-after=<marker>]
                   [ --stdin | <pattern>... ]
+git refs exists <ref>
 
 DESCRIPTION
 -----------
@@ -38,6 +39,12 @@ list::
        formatting, and sorting. This subcommand is an alias for
        linkgit:git-for-each-ref[1] and offers identical functionality.
 
+exists::
+       Check whether the given reference exists. Returns an exit code of 0 if
+       it does, 2 if it is missing, and 1 in case looking up the reference
+       failed with an error other than the reference being missing. This does
+       not verify whether the reference resolves to an actual object.
+
 OPTIONS
 -------
 

diff --git a/builtin/refs.c b/builtin/refs.c
index 76224feba4d55a0ff2908df51eb2eb264f9fb962..91548783b75b589b957bf0cce8f5b425ffab56fb 100644 (file)
--- a/builtin/refs.c
+++ b/builtin/refs.c
@@ -7,6 +7,7 @@
 #include "strbuf.h"
 #include "worktree.h"
 #include "for-each-ref.h"
+#include "refs/refs-internal.h"
 
 #define REFS_MIGRATE_USAGE \
        N_("git refs migrate --ref-format=<format> [--no-reflog] [--dry-run]")
@@ -14,6 +15,9 @@
 #define REFS_VERIFY_USAGE \
        N_("git refs verify [--strict] [--verbose]")
 
+#define REFS_EXISTS_USAGE \
+       N_("git refs exists <ref>")
+
 static int cmd_refs_migrate(int argc, const char **argv, const char *prefix,
                            struct repository *repo UNUSED)
 {
@@ -113,6 +117,48 @@ static int cmd_refs_list(int argc, const char **argv, const char *prefix,
        return for_each_ref_core(argc, argv, prefix, repo, refs_list_usage);
 }
 
+static int cmd_refs_exists(int argc, const char **argv, const char *prefix,
+                          struct repository *repo UNUSED)
+{
+       struct strbuf unused_referent = STRBUF_INIT;
+       struct object_id unused_oid;
+       unsigned int unused_type;
+       int failure_errno = 0;
+       const char *ref;
+       int ret = 0;
+       const char * const exists_usage[] = {
+               REFS_EXISTS_USAGE,
+               NULL,
+       };
+       struct option options[] = {
+               OPT_END(),
+       };
+
+       argc = parse_options(argc, argv, prefix, options, exists_usage, 0);
+       if (argc != 1)
+               die(_("'git refs exists' requires a reference"));
+
+       ref = *argv++;
+       if (refs_read_raw_ref(get_main_ref_store(the_repository), ref,
+                             &unused_oid, &unused_referent, &unused_type,
+                             &failure_errno)) {
+               if (failure_errno == ENOENT || failure_errno == EISDIR) {
+                       error(_("reference does not exist"));
+                       ret = 2;
+               } else {
+                       errno = failure_errno;
+                       error_errno(_("failed to look up reference"));
+                       ret = 1;
+               }
+
+               goto out;
+       }
+
+out:
+       strbuf_release(&unused_referent);
+       return ret;
+}
+
 int cmd_refs(int argc,
             const char **argv,
             const char *prefix,
@@ -122,6 +168,7 @@ int cmd_refs(int argc,
                REFS_MIGRATE_USAGE,
                REFS_VERIFY_USAGE,
                "git refs list " COMMON_USAGE_FOR_EACH_REF,
+               REFS_EXISTS_USAGE,
                NULL,
        };
        parse_opt_subcommand_fn *fn = NULL;
@@ -129,6 +176,7 @@ int cmd_refs(int argc,
                OPT_SUBCOMMAND("migrate", &fn, cmd_refs_migrate),
                OPT_SUBCOMMAND("verify", &fn, cmd_refs_verify),
                OPT_SUBCOMMAND("list", &fn, cmd_refs_list),
+               OPT_SUBCOMMAND("exists", &fn, cmd_refs_exists),
                OPT_END(),
        };