Subject: Re: [PATCH v3 1/4] Documentation/git-bundle.txt: mention full backup example

From: Junio C Hamano <[email-masked]>
Date: Fri, 08 Nov 2024 11:01:56 +0900

[email-masked] writes:

> +We'll discuss two cases:
> +
> +1. Taking a full backup of a repository
> +2. Transfer the history of a repository to another machine when the two
> +   machines have no direct connection

Contrasting (1) taking a backup and (2) extracting a backup later is
a very useful way to frame the problem, but then, I'd say

 1. taking a backup, either full or incremental, of a repository

 2. using the backup, either full or incremental, to transfer the
    history of the origin repository to any repository (including
    itself) without needing any other connection between the two
    repositories.

Whether a full or an incremental, the resulting bundle file can be
used as an offline medium and then later extracted elsewhere, even
if there is no direct network connection between the origin
repository and the destination repository.  But you can extract in
the origin repository as well.

But that would require a bit more surgery to the presentation order
of the text, so I do not mind deferrring it to a later and separate
series.  If we were to go that route, it would be helpful to have a
paragraph to describe how you use your "full backup" bundle to recover
lost data from, though.  To those of us who know what is happening,
there is not much difference between the extraction side of the
sneaker-net example, but as we framed the use in two distinct cases,
it would be helpful to make each case stand on its own.

> +First let's consider a full backup of the repository.  The following
> +command will take a full backup of the repository in the sense that all
> +refs are included in the bundle (except `refs/stash`, i.e. the stash):

Are you sure the "except" part is factually correct?

I did

    $ git bundle create x.bndl --all && git ls-remote x.bndl |
      grep stash

and I see refs/stash listed there just fine.  You should be able to
extract them all with

    $ git clone --mirror x.bndl xxx && cd xxx && git for-each-ref |
      grep stash

and see that refs/stash gets propagated.

Fix is a simple s/except/including/ ;-)

> +----------------
> +$ git bundle create <file> --all
> +----------------
> +
> +But note again that this is only for the refs, i.e. you will only
> +include refs and commits reachable from those refs.  You will not
> +include other local state, such as the contents of the index, working
> +tree, per-repository configuration, hooks, etc.

And to make each case stand on its own, we would want to teach
readers how to use the full backup to recover data from here, before
moving on to the "next example".

    You can use the resulting bundle file as if it is a repository,
    a snapshot of it at the time the bundle was created.  You can
    use

    ---
    $ git ls-remote full.bndl
    ---

    to inspect what refs are recorded in it, and you can fetch from or
    even merge a branch out of it, with commands like:

    ---
    $ git fetch full.bndl my-butchered-topic
    $ git show-branch my-butchered-topic FETCH_HEAD
    $ git branch -f my-butchered-topic FETCH_HEAD
    $ git pull full.bndl  my-butchered-topic
    ---

    after you screwed up one of your branches and resurrect it from
    the backup.

or something like that.

> +For the next example, assume you want to transfer the history from a
> +repository R1 on machine A to another repository R2 on machine B.
>  For whatever reason, direct connection between A and B is not allowed,
>  but we can move data from A to B via some mechanism (CD, email, etc.).
>  We want to update R2 with development made on the branch master in R1.