Hi David,
David Barr writes:
> As the description of the "progress" option in git-fast-import.1
> hints, there is no convenient way to immediately access the blobs
> written to a new repository through fast-import. Until a checkpoint
> has been started and finishes writing the pack index, any new blobs
> will not be accessible using standard git tools.
>
> So introduce another way: a "cat-blob" command introduced in the
> command stream requests for fast-import to print a blob to stdout
> or a file descriptor specified by the argument --cat-blob-fd.
>
> The output uses the same format as "git cat-file --batch".
Nice :) It looks like we finally have a nice polished version.
Caution: Most of the review are just notes to self, or style
nitpicks. Feel free to ignore.
> Cc: Shawn O. Pearce <spearce@xxxxxxxxxxx>
> Cc: Ramkumar Ramachandra <artagnon@xxxxxxxxx>
> Helped-by: Sverre Rabbelier <srabbelier@xxxxxxxxx>
> Based-on-patch-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
> Signed-off-by: David Barr <david.barr@xxxxxxxxxxxx>
> ---
> Documentation/git-fast-import.txt | 34 ++++++++++++++
> fast-import.c | 92 +++++++++++++++++++++++++++++++++++++
> 2 files changed, 126 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt
> index 966ba4f..42a100b 100644
> --- a/Documentation/git-fast-import.txt
> +++ b/Documentation/git-fast-import.txt
> @@ -92,6 +92,17 @@ OPTIONS
> --(no-)-relative-marks= with the --(import|export)-marks=
> options.
>
> +--cat-blob-fd=<fd>::
> + Specify the file descriptor that will be written to
> + when the `cat-blob` command is encountered in the stream.
> + The default behaviour is to write to `stdout`.
> ++
> +The described objects are not necessarily accessible
> +using standard git plumbing tools until a little while
> +after the next checkpoint. To request access to the
> +blobs before then, use `cat-blob` lines in the command
> +stream.
> +
> --export-pack-edges=<file>::
> After creating a packfile, print a line of data to
> <file> listing the filename of the packfile and the last
> @@ -320,6 +331,11 @@ and control the current import process. More detailed discussion
> standard output. This command is optional and is not needed
> to perform an import.
>
> +`cat-blob`::
> + Causes fast-import to print a blob in 'cat-file --batch'
> + format to the file descriptor set with `--cat-blob-fd` or
> + `stdout` if unspecified.
> +
> `feature`::
> Require that fast-import supports the specified feature, or
> abort if it does not.
> @@ -876,6 +892,23 @@ Placing a `progress` command immediately after a `checkpoint` will
> inform the reader when the `checkpoint` has been completed and it
> can safely access the refs that fast-import updated.
>
> +`cat-blob`
> +~~~~~
> +Causes fast-import to print a blob to a file descriptor previously
> +arranged with the `--cat-blob-fd` argument. The command otherwise
> +has no impact on the current import; its main purpose is to
> +retrieve blobs that may be in fast-import's memory but not
> +accessible from the target repository a little quicker than by the
> +method suggested by the description of the `progress` option.
> +
> +....
> + 'cat-blob' SP <dataref> LF
> +....
> +
> +The `<dataref>` can be either a mark reference (`:<idnum>`)
> +set previously, or a full 40-byte SHA-1 of any Git blob,
> +preexisting or ready to be written.
> +
> `feature`
> ~~~~~~~~~
> Require that fast-import supports the specified feature, or abort if
> @@ -896,6 +929,7 @@ The following features are currently supported:
> * date-format
> * import-marks
> * export-marks
> +* cat-blob
> * relative-marks
> * no-relative-marks
> * force
Looks perfect.
> diff --git a/fast-import.c b/fast-import.c
> index 2317b0f..ea3e529 100644
> --- a/fast-import.c
> +++ b/fast-import.c
> @@ -55,6 +55,8 @@ Format of STDIN stream:
> ('from' sp committish lf)?
> lf?;
>
> + cat_blob ::= 'cat-blob' sp (hexsha1 | idnum) lf;
> +
> checkpoint ::= 'checkpoint' lf
> lf?;
>
> @@ -361,6 +363,9 @@ static uintmax_t next_mark;
> static struct strbuf new_data = STRBUF_INIT;
> static int seen_data_command;
>
> +/* Where to write output of cat-blob commands */
> +static int cat_blob_fd = 1;
> +
Right. Defaults to stdout, as described in documentation.
> static void parse_argv(void);
>
> static void write_branch_report(FILE *rpt, struct branch *b)
> @@ -2680,6 +2685,77 @@ static void parse_reset_branch(void)
> unread_command_buf = 1;
> }
>
> +static void cat_blob_write(const char *buf, unsigned long size)
> +{
> + if (write_in_full(cat_blob_fd, buf, size) != size)
> + die_errno("Write to frontend failed");
> +}
Note to self: I didn't notice write_in_full in wrapper.c
earlier. Returns the actual size written to the fd from the buffer.
> +static void cat_blob(struct object_entry *oe, unsigned char sha1[20])
> +{
> + struct strbuf line = STRBUF_INIT;
> + unsigned long size;
> + enum object_type type = 0;
> + char *buf;
> +
> + if (oe && oe->pack_id != MAX_PACK_ID) {
> + type = oe->type;
> + buf = gfi_unpack_entry(oe, &size);
> + } else {
> + buf = read_sha1_file(sha1, &type, &size);
> + }
> + if (!buf)
> + die("Can't read object %s", sha1_to_hex(sha1));
Ok. Looks similar enough to the code in the other functions.
> +
> + /*
> + * Output based on batch_one_object() from cat-file.c.
> + */
> + if (type <= 0) {
> + strbuf_reset(&line);
> + strbuf_addf(&line, "%s missing\n", sha1_to_hex(sha1));
> + cat_blob_write(line.buf, line.len);
> + return;
> + } else if (type != OBJ_BLOB) {
> + die("Object %s is a %s but a blob was expected.",
> + sha1_to_hex(sha1), typename(type));
> + }
> + strbuf_reset(&line);
> + strbuf_addf(&line, "%s %s %lu\n", sha1_to_hex(sha1),
> + typename(type), size);
> + cat_blob_write(line.buf, line.len);
> + cat_blob_write(buf, size);
> + cat_blob_write("\n", 1);
> + free(buf);
Cool.
> +}
> +
> +
> +static void parse_cat_blob(void)
> +{
> + const char *p;
> + struct object_entry *oe = oe;
> + unsigned char sha1[20];
> +
> + /* cat SP <object> */
> + p = command_buf.buf + strlen("cat-blob ");
> + if (*p == ':') {
> + char *x;
> + oe = find_mark(strtoumax(p + 1, &x, 10));
> + if (x == p + 1)
> + die("Invalid mark: %s", command_buf.buf);
> + if (!oe)
> + die("Unknown mark: %s", command_buf.buf);
> + p = x;
> + hashcpy(sha1, oe->idx.sha1);
The mark case.
> + } else {
> + if (get_sha1_hex(p, sha1))
> + die("Invalid SHA1: %s", command_buf.buf);
> + p += 40;
> + oe = find_object(sha1);
> + }
The SHA1 case.
Looks similar enough to the code in the other functions.
> +
> + cat_blob(oe, sha1);
> +}
> +
> static void parse_checkpoint(void)
> {
> if (object_count) {
> @@ -2755,6 +2831,14 @@ static void option_export_marks(const char *marks)
> safe_create_leading_directories_const(export_marks_file);
> }
>
> +static void option_cat_blob_fd(const char *fd)
> +{
> + unsigned long n = strtoul(fd, NULL, 0);
> + if (n > (unsigned long) INT_MAX)
> + die("--cat-blob-fd cannot exceed %d", INT_MAX);
> + cat_blob_fd = (int) n;
> +}
> +
You don't display an appropriate error when n < 0.
> static void option_export_pack_edges(const char *edges)
> {
> if (pack_edges)
> @@ -2808,6 +2892,8 @@ static int parse_one_feature(const char *feature, int from_stream)
> option_import_marks(feature + 13, from_stream);
> } else if (!prefixcmp(feature, "export-marks=")) {
> option_export_marks(feature + 13);
> + } else if (!prefixcmp(feature, "cat-blob")) {
> + /* Don't die - this feature is supported */
Style nit: There are no statements in this branch. Maybe put a
semicolon?
> } else if (!prefixcmp(feature, "relative-marks")) {
> relative_marks_paths = 1;
> } else if (!prefixcmp(feature, "no-relative-marks")) {
> @@ -2896,6 +2982,10 @@ static void parse_argv(void)
> if (*a != '-' || !strcmp(a, "--"))
> break;
>
> + if (!prefixcmp(a + 2, "cat-blob-fd=")) {
> + option_cat_blob_fd(a + 2 + 12);
> + }
> +
Style nit: Unnecessary braces around `if` statement.
> if (parse_one_option(a + 2))
> continue;
>
> @@ -2953,6 +3043,8 @@ int main(int argc, const char **argv)
> parse_new_tag();
> else if (!prefixcmp(command_buf.buf, "reset "))
> parse_reset_branch();
> + else if (!prefixcmp(command_buf.buf, "cat-blob "))
> + parse_cat_blob();
> else if (!strcmp("checkpoint", command_buf.buf))
> parse_checkpoint();
> else if (!prefixcmp(command_buf.buf, "progress "))
> --
> 1.7.3.32.g634ef
>
Ok. I'm eager to see this go through to `master`.
Reviewed-by: Ramkumar Ramachandra <artagnon@xxxxxxxxx>
-- Ram
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