On 25 Jan 2022, at 17:50, John Cai wrote: > This RFC patch proposes a new flag --stdin-cmd that works with > git-cat-file --batch. Similar to git-update-ref --stdin, it will accept > commands and arguments from stdin. Sorry I forgot to change this summary. s/--stdin-cmd/--batch-command > > The start of this idea was discussed in [1], where the original > motivation was to be able to control when the buffer was flushed to > stdout in --buffer mode. > > However, this can actually be much more useful in situations when > git-cat-file --batch is being used as a long lived backend query > process. At GitLab, we use a pair of cat-file processes. One for > iterating over object metadata with --batch-check, and the other to grab > object contents with --batch. However, if we had --stdin-cmd, we could > get rid of the second --batch-check process, and just have one progress > where we can flip between getting object info, and getting object contents. > This can lead to huge savings. > > git cat-file --batch --stdin-cmd > > $ <command> [arg1] [arg2] NL > > We can also add a -z mode to allow for NUL-terminated lines > > $ <command> [arg1] [arg2] NUL > > This patch adds three commands: object, info, fflush > > $ object <sha1> NL > $ info <sha1> NL > $ fflush NL > > These three would be immediately useful in GitLab's context, but one can > imagine this mode to be further extended for other things. > > For instance, a non-trivial part of "cat-file --batch" time is spent > on parsing its argument and seeing if it's a revision, ref etc. So we > could add a command that only accepts a full-length 40 > character SHA-1. > > This would be the first step in adding such an interface to > git-cat-file. > > [1] https://lore.kernel.org/git/pull.1124.git.git.1636149400.gitgitgadget@xxxxxxxxx/ > > Helped-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> > Signed-off-by: John Cai <johncai86@xxxxxxxxx> > --- > Changes from v1: > > - changed option name to batch-command. > - changed command function interface to receive the whole line after the command > name to put the onus of parsing arguments to each individual command function. > - pass in whole line to batch_one_object in both parse_cmd_object and > parse_cmd_info to support spaces in the object reference. > - removed addition of -z to include in a separate patch series > - added documentation. > --- > Documentation/git-cat-file.txt | 15 +++++ > builtin/cat-file.c | 114 ++++++++++++++++++++++++++++++++- > strvec.c | 23 +++++++ > strvec.h | 8 +++ > t/t1006-cat-file.sh | 32 +++++++++ > 5 files changed, 191 insertions(+), 1 deletion(-) > > diff --git a/Documentation/git-cat-file.txt b/Documentation/git-cat-file.txt > index bef76f4dd0..8aefa45e4c 100644 > --- a/Documentation/git-cat-file.txt > +++ b/Documentation/git-cat-file.txt > @@ -96,6 +96,21 @@ OPTIONS > need to specify the path, separated by whitespace. See the > section `BATCH OUTPUT` below for details. > > +-batch-command:: > + Enter a command mode that reads from stdin. May not be combined with any > + other options or arguments except `--textconv` or `--filters`, in which > + case the input lines also need to specify the path, separated by > + whitespace. See the section `BATCH OUTPUT` below for details. > + > +object <object>:: > + Print object contents for object reference <object> > + > +info <object>:: > + Print object info for object reference <object> > + > +flush:: > + Flush to stdout immediately when used with --buffer > + > --batch-all-objects:: > Instead of reading a list of objects on stdin, perform the > requested batch operation on all objects in the repository and > diff --git a/builtin/cat-file.c b/builtin/cat-file.c > index 7b3f42950e..30794284d5 100644 > --- a/builtin/cat-file.c > +++ b/builtin/cat-file.c > @@ -16,6 +16,7 @@ > #include "packfile.h" > #include "object-store.h" > #include "promisor-remote.h" > +#include "strvec.h" > > struct batch_options { > int enabled; > @@ -26,7 +27,10 @@ struct batch_options { > int unordered; > int cmdmode; /* may be 'w' or 'c' for --filters or --textconv */ > const char *format; > + int stdin_cmd; > + int end_null; > }; > +static char line_termination = '\n'; > > static const char *force_path; > > @@ -508,6 +512,102 @@ static int batch_unordered_packed(const struct object_id *oid, > data); > } > > +enum batch_state { > + /* Non-transactional state open for commands. */ > + BATCH_STATE_OPEN, > +}; > + > +static void parse_cmd_object(struct batch_options *opt, > + const char *line, > + struct strbuf *output, > + struct expand_data *data) > +{ > + opt->print_contents = 1; > + batch_one_object(line, output, opt, data); > +} > + > +static void parse_cmd_info(struct batch_options *opt, > + const char *line, > + struct strbuf *output, > + struct expand_data *data) > +{ > + opt->print_contents = 0; > + batch_one_object(line, output, opt, data); > +} > + > +static void parse_cmd_fflush(struct batch_options *opt, > + const char *line, > + struct strbuf *output, > + struct expand_data *data) > +{ > + fflush(stdout); > +} > + > +typedef void (*parse_cmd_fn_t)(struct batch_options *, const char *, > + struct strbuf *, struct expand_data *); > + > +static const struct parse_cmd { > + const char *prefix; > + parse_cmd_fn_t fn; > + unsigned args; > + enum batch_state state; > +} commands[] = { > + { "object", parse_cmd_object, 1, BATCH_STATE_OPEN }, > + { "info", parse_cmd_info, 1, BATCH_STATE_OPEN }, > + { "fflush", parse_cmd_fflush, 0, BATCH_STATE_OPEN }, > +}; > + > +static void batch_objects_stdin_cmd(struct batch_options *opt, > + struct strbuf *output, > + struct expand_data *data) > +{ > + struct strbuf input = STRBUF_INIT; > + enum batch_state state = BATCH_STATE_OPEN; > + > + /* Read each line dispatch its command */ > + while (!strbuf_getwholeline(&input, stdin, line_termination)) { > + int i; > + const struct parse_cmd *cmd = NULL; > + const char *p; > + > + if (*input.buf == line_termination) > + die("empty command in input"); > + else if (isspace(*input.buf)) > + die("whitespace before command: %s", input.buf); > + > + for (i = 0; i < ARRAY_SIZE(commands); i++) { > + const char *prefix = commands[i].prefix; > + char c; > + const char *cmd_name; > + if (!skip_prefix(input.buf, prefix, &cmd_name)) > + continue; > + /* > + * If the command has arguments, verify that it's > + * followed by a space. Otherwise, it shall be followed > + * by a line terminator. > + */ > + c = commands[i].args ? ' ' : line_termination; > + if (input.buf[strlen(prefix)] != c) > + continue; > + > + cmd = &commands[i]; > + break; > + } > + if (!cmd) > + die("unknown command: %s", input.buf); > + > + p = input.buf + strlen(cmd->prefix) + 1; > + const char *pos = strstr(p, &line_termination); > + > + switch (state) { > + case BATCH_STATE_OPEN: > + break; > + } > + cmd->fn(opt, xstrndup(p, pos-p), output, data); > + } > + strbuf_release(&input); > +} > + > static int batch_objects(struct batch_options *opt) > { > struct strbuf input = STRBUF_INIT; > @@ -515,6 +615,7 @@ static int batch_objects(struct batch_options *opt) > struct expand_data data; > int save_warning; > int retval = 0; > + const int stdin_cmd = opt->stdin_cmd; > > if (!opt->format) > opt->format = "%(objectname) %(objecttype) %(objectsize)"; > @@ -590,7 +691,8 @@ static int batch_objects(struct batch_options *opt) > save_warning = warn_on_object_refname_ambiguity; > warn_on_object_refname_ambiguity = 0; > > - while (strbuf_getline(&input, stdin) != EOF) { > + while (!stdin_cmd && > + strbuf_getline(&input, stdin) != EOF) { > if (data.split_on_whitespace) { > /* > * Split at first whitespace, tying off the beginning > @@ -608,6 +710,9 @@ static int batch_objects(struct batch_options *opt) > batch_one_object(input.buf, &output, opt, &data); > } > > + if (stdin_cmd) > + batch_objects_stdin_cmd(opt, &output, &data); > + > strbuf_release(&input); > strbuf_release(&output); > warn_on_object_refname_ambiguity = save_warning; > @@ -636,6 +741,7 @@ static int batch_option_callback(const struct option *opt, > > bo->enabled = 1; > bo->print_contents = !strcmp(opt->long_name, "batch"); > + bo->stdin_cmd = !strcmp(opt->long_name, "batch-command"); > bo->format = arg; > > return 0; > @@ -683,6 +789,10 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix) > N_("like --batch, but don't emit <contents>"), > PARSE_OPT_OPTARG | PARSE_OPT_NONEG, > batch_option_callback), > + OPT_CALLBACK_F(0, "batch-command", &batch, N_(""), > + N_("enters batch mode that accepts commands"), > + PARSE_OPT_NOARG | PARSE_OPT_NONEG, > + batch_option_callback), > OPT_CMDMODE(0, "batch-all-objects", &opt, > N_("with --batch[-check]: ignores stdin, batches all known objects"), 'b'), > /* Batch-specific options */ > @@ -738,6 +848,8 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix) > /* Batch defaults */ > if (batch.buffer_output < 0) > batch.buffer_output = batch.all_objects; > + if (batch.end_null) > + line_termination = '\0'; > > /* Return early if we're in batch mode? */ > if (batch.enabled) { > diff --git a/strvec.c b/strvec.c > index 61a76ce6cb..7dca04bf7a 100644 > --- a/strvec.c > +++ b/strvec.c > @@ -85,6 +85,29 @@ void strvec_split(struct strvec *array, const char *to_split) > } > } > > +size_t strvec_split_delim(struct strvec *array, const char *string, > + int delim, int maxsplit) > +{ > + size_t count = 0; > + const char *p = string, *end; > + > + for (;;) { > + count++; > + if (maxsplit >= 0 && count > maxsplit) { > + strvec_push(array, p); > + return count; > + } > + end = strchr(p, delim); > + if (end) { > + strvec_push_nodup(array, xmemdupz(p, end - p)); > + p = end + 1; > + } else { > + strvec_push(array, p); > + return count; > + } > + } > +} > + > void strvec_clear(struct strvec *array) > { > if (array->v != empty_strvec) { > diff --git a/strvec.h b/strvec.h > index 9f55c8766b..c474918b91 100644 > --- a/strvec.h > +++ b/strvec.h > @@ -73,6 +73,14 @@ void strvec_pop(struct strvec *); > /* Splits by whitespace; does not handle quoted arguments! */ > void strvec_split(struct strvec *, const char *); > > +/** > + * strvec_split_delim() is a split function that behaves more like its > + * string_list_split() cousin than the whitespace-splitting > + * strvec_split(). > + */ > +size_t strvec_split_delim(struct strvec *array, const char *string, > + int delim, int maxsplit); > + > /** > * Free all memory associated with the array and return it to the > * initial, empty state. > diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh > index 145eee11df..935ab1cd34 100755 > --- a/t/t1006-cat-file.sh > +++ b/t/t1006-cat-file.sh > @@ -964,4 +964,36 @@ test_expect_success 'cat-file --batch-all-objects --batch-check ignores replace' > test_cmp expect actual > ' > > +F='%s\0' > + > +test_expect_success 'batch-command unknown command' ' > + echo unknown_command >cmd && > + test_expect_code 128 git cat-file --batch-command < cmd 2>err && > + grep -E "^fatal:.*unknown command.*" err > +' > + > +test_expect_success 'setup object data' ' > + content="Object Data" && > + size=$(strlen "$content") && > + sha1=$(echo_without_newline "$content" | git hash-object -w --stdin) > +' > + > +test_expect_success 'batch-command calling object works' ' > + echo "object $sha1" | git cat-file --batch-command >actual && > + echo "$sha1 blob $size" >expect && > + echo `git cat-file -p "$sha1"` >>expect && > + test_cmp expect actual > +' > + > +test_expect_success 'batch-command calling info works' ' > + echo "info $sha1" | git cat-file --batch-command >actual && > + echo "$sha1 blob $size" >expect && > + test_cmp expect actual > +' > + > +test_expect_success 'batch-command fflush works' ' > + printf "fflush\n" > cmd && > + test_expect_code 0 git cat-file --batch-command < cmd 2>err > +' > + > test_done > -- > 2.34.1
