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ls-tree: support --object-only option for "git-ls-tree"

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'--object-only' is an alias for '--format=%(objectname)'. It cannot
be used together other format-altering options like '--name-only',
'--long' or '--format', they are mutually exclusive.

The "--name-only" option outputs <filepath> only. Likewise, <objectName>
is another high frequency used field, so implement '--object-only' option
will bring intuitive and clear semantics for this scenario. Using
'--format=%(objectname)' we can achieve a similar effect, but the former
is with a lower learning cost(without knowing the format requirement
of '--format' option).

Even so, if a user is prefer to use "--format=%(objectname)", this is entirely
welcome because they are not only equivalent in function, but also have almost
identical performance. The reason is this commit also add the specific of
"--format=%(objectname)" to the current fast-pathes (builtin formats) to
avoid running unnecessary parsing mechanisms.

The following performance benchmarks are based on torvalds/linux.git:

  When hit the fast-path:

      Benchmark 1: /opt/git/ls-tree-oid-only/bin/git ls-tree -r --object-only HEAD
        Time (mean ± σ):      83.6 ms ±   2.0 ms    [User: 59.4 ms, System: 24.1 ms]
        Range (min … max):    80.4 ms …  87.2 ms    35 runs

      Benchmark 1: /opt/git/ls-tree-oid-only/bin/git ls-tree -r --format='%(objectname)' HEAD
        Time (mean ± σ):      84.1 ms ±   1.8 ms    [User: 61.7 ms, System: 22.3 ms]
        Range (min … max):    80.9 ms …  87.5 ms    35 runs

  But for a customized format, it will be slower:

       Benchmark 1: /opt/git/ls-tree-oid-only/bin/git ls-tree -r --format='oid: %(objectname)' HEAD
         Time (mean ± σ):      96.5 ms ±   2.5 ms    [User: 72.9 ms, System: 23.5 ms]
  	 Range (min … max):    93.1 ms … 104.1 ms    31 runs

Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Teng Long <dyroneteng@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Teng Long
2022-03-23 17:13:13 +08:00
committed by Junio C Hamano
parent 455923e0a1
commit cab851c2f8
4 changed files with 36 additions and 4 deletions
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13
builtin/ls-tree.c
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@ -24,7 +24,6 @@ static struct pathspec pathspec;
static int chomp_prefix;
static const char *ls_tree_prefix;
static const char *format;
struct show_tree_data {
unsigned mode;
enum object_type type;
@ -42,6 +41,7 @@ static enum ls_tree_cmdmode {
MODE_DEFAULT = 0,
MODE_LONG,
MODE_NAME_ONLY,
MODE_OBJECT_ONLY,
} cmdmode;
static void expand_objectsize(struct strbuf *line, const struct object_id *oid,
@ -227,6 +227,11 @@ static int show_tree(const struct object_id *oid, struct strbuf *base,
return recurse;
}
if (cmdmode == MODE_OBJECT_ONLY) {
printf("%s%c", find_unique_abbrev(oid, abbrev), line_termination);
return recurse;
}
if (cmdmode == MODE_NAME_ONLY) {
baselen = base->len;
strbuf_addstr(base, pathname);
@ -264,6 +269,10 @@ static struct ls_tree_cmdmode_to_fmt ls_tree_cmdmode_format[] = {
.mode = MODE_NAME_ONLY, /* And MODE_NAME_STATUS */
.fmt = "%(path)",
},
{
.mode = MODE_OBJECT_ONLY,
.fmt = "%(objectname)",
},
{ 0 },
};
@ -288,6 +297,8 @@ int cmd_ls_tree(int argc, const char **argv, const char *prefix)
MODE_NAME_ONLY),
OPT_CMDMODE(0, "name-status", &cmdmode, N_("list only filenames"),
MODE_NAME_ONLY),
OPT_CMDMODE(0, "object-only", &cmdmode, N_("list only objects"),
MODE_OBJECT_ONLY),
OPT_SET_INT(0, "full-name", &chomp_prefix,
N_("use full path names"), 0),
OPT_BOOL(0, "full-tree", &full_tree,