From: Junio C Hamano <firstname.lastname@example.org>
To: Masaya Suzuki <email@example.com>
Subject: Re: [PATCH] doc: describe Git bundle format
Date: Fri, 31 Jan 2020 12:38:27 -0800 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
In-Reply-To: <email@example.com> (Masaya Suzuki's message of "Thu, 30 Jan 2020 14:58:18 -0800")
Masaya Suzuki <firstname.lastname@example.org> writes:
> The bundle format was not documented. Describe the format with ABNF and
> explain the meaning of each part.
> Signed-off-by: Masaya Suzuki <email@example.com>
> Documentation/technical/bundle-format.txt | 40 +++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
> create mode 100644 Documentation/technical/bundle-format.txt
> diff --git a/Documentation/technical/bundle-format.txt b/Documentation/technical/bundle-format.txt
> new file mode 100644
> index 0000000000..dbb80225b5
> --- /dev/null
> +++ b/Documentation/technical/bundle-format.txt
> @@ -0,0 +1,40 @@
> += Git bundle v2 format
> +The Git bundle format is a format that represents both refs and Git objects.
> +== Format
> +We will use ABNF notation to define the Git bundle format. See
> +protocol-common.txt for the details.
> +bundle = signature references pack
> +signature = "# v2 git bundle" LF
Good. "signature" is the name used by bundle.c::create_bundle() to
call this part.
> +references = *(prerequisite / ref) LF
This allows prereq and ref can come inter-mixed, but I think we show
all prerequisites first before refs.
> +prerequisite = "-" obj-id SP comment LF
> +comment = *CHAR
Do readers know what CHAR consists of? Anything other than NUL and
> +ref = obj-id SP refname LF
"prerequisite" and "ref" are both used in bundle.c::create_bundle(),
so calling these parts with these names is consistent with the code.
"head" is also a good name for the latter as "git bundle list-heads"
is the way the end-users access them from outside.
> +pack = ... ; packfile
> +== Semantics
> +A Git bundle consists of three parts.
> +* Prerequisites: Optional list of objects that are not included in the bundle
> + file. A bundle can reference these prerequisite objects (or it can reference
> + the objects reachable from the prerequisite objects). The bundle itself
> + might not contain those objects.
While not incorrect per-se, the above misses the more important
points (and defers the description to a later paragraph). It is
better to describe what it means to have prereqs upfront.
> +* References: Mapping of ref names to objects.
> +* Git objects: Commit, tree, blob, and tags. These are included in the pack
> + format.
Match the name you used to descibe the parts in the earlier ABNF
description, so that the correspondence is clear to the readers.
You somehow used "references" to mean both prereqs and heads, but in
the above you are describing only "heads" under the label of
Perhaps something like this?
* "Prerequisites" lists the objects that are NOT included in the
bundle and the receiver of the bundle MUST already have, in
order to use the data in the bundle. The objects stored in
the bundle may refer to prerequiste objects and anything
reachable from them and/or expressed as a delta against
* "Heads" record the tips of the history graph, iow, what the
receiver of the bundle CAN "git fetch" from it.
* "Pack" is the pack data stream "git fetch" would send, if you
fetch from a repository that has the references recorded in
the "Heads" above into a repository that has references
pointing at the objects listed in "Prerequisites" above.
> +If a bundle contains prerequisites, it means the bundle has a thin pack and the
> +bundle alone is not enough for resolving all objects. When you read such
> +bundles, you should have those missing objects beforehand.
With the above rewrite, this paragraph is unneeded.
> +In the bundle format, there can be a comment following a prerequisite obj-id.
> +This is a comment and it has no specific meaning. When you write a bundle, you
> +can put any string here. When you read a bundle, you can ignore this part.
Is it "you can"? At least the last one should be "readers of a
bundle MUST ignore the comment", I think.
next prev parent reply other threads:[~2020-01-31 20:38 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 22:58 [PATCH] doc: describe Git bundle format Masaya Suzuki
2020-01-31 13:56 ` Johannes Schindelin
2020-01-31 20:38 ` Junio C Hamano [this message]
2020-01-31 21:49 ` Masaya Suzuki
2020-01-31 23:01 ` Junio C Hamano
2020-01-31 23:57 ` Masaya Suzuki
2020-02-04 18:20 ` Junio C Hamano
2020-01-31 22:18 ` [PATCH v2] " Masaya Suzuki
2020-01-31 23:06 ` Junio C Hamano
2020-02-07 20:42 ` [PATCH v3] " Masaya Suzuki
2020-02-07 20:44 ` Masaya Suzuki
2020-02-07 20:59 ` Junio C Hamano
2020-02-07 22:21 ` Masaya Suzuki
2020-02-08 1:49 ` Junio C Hamano
2020-02-12 22:13 ` Masaya Suzuki
2020-02-12 22:43 ` Junio C Hamano
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).