Re: [RFC v2] submodule: Respect requested branch on all clones

From: W. Trevor King <wking@tremily.us>
Date: Jan 6, 2014, 01:12 UTC
Message-ID: <20140106011255.GM3156@odin.tremily.us>
In-Reply-To: <20140106003314.GL3156@odin.tremily.us>

On Sun, Jan 05, 2014 at 04:33:14PM -0800, W. Trevor King wrote:

Show 6 quoted lines

> The only people who would need *automatic* rebase recovery would be
> superproject devs update-cloning the subproject.  That's a small
> enough cross-section that I don't think it deserves the ambiguity of
> gitlink-to-reference.  In that case, all you really need is a way to
> force a recovery gitlink (i.e. add a 'commit' object to the tree by
> hand).

Actually, you recovering by hand is a lot easier. Setup a rebased-away gitlink target:

  mkdir subproject &&
  (
    cd subproject &&
    git init
    echo 'Subproject' > README &&
    git add README &&
    git commit -m 'Subproject v1' &&
    echo 'Changes' >> README &&
    git commit -am 'Subproject v2'
  ) &&
  mkdir superproject &&
  (
    cd superproject &&
    git init
    git submodule add ../subproject &&
    git commit -m 'Superproject v1'
  ) &&
  (
    cd subproject &&
    git reset --hard HEAD^ &&
    git reflog expire --expire=now --all &&
    git gc --aggressive --prune=now
  )

Then a recursive clone of the superproject dies:

  $ git clone --recursive superproject super2
  Cloning into 'super2'...
  done.
  Submodule 'subproject' (/tmp/x/subproject) registered for path 'subproject'
  Cloning into 'subproject'...
  done.
  fatal: reference is not a tree: f589144d16282d1a80d17a9032c6f1d332e38dd0
  Unable to checkout 'f589144d16282d1a80d17a9032c6f1d332e38dd0' in submodule path 'subproject'

But you still have the submodule checkout (up until the $sha1 setup):

  $ cd super2
  $ git diff
  diff --git a/subproject b/subproject
  index f589144..82d4553 160000
  --- a/subproject
  +++ b/subproject
  @@ -1 +1 @@
  -Subproject commit f589144d16282d1a80d17a9032c6f1d332e38dd0
  +Subproject commit 82d4553fe437ae014f22bbc87a082c6d19e5d9f9-dirty

And you can automatically update to match the upstream remote:

  $ git submodule update --remote --force
  Submodule path 'subproject': checked out '82d4553fe437ae014f22bbc87a082c6d19e5d9f9'
  $ git diff
  diff --git a/subproject b/subproject
  index f589144..82d4553 160000
  --- a/subproject
  +++ b/subproject
  @@ -1 +1 @@
  -Subproject commit f589144d16282d1a80d17a9032c6f1d332e38dd0
  +Subproject commit 82d4553fe437ae014f22bbc87a082c6d19e5d9f9

When explicitly updating to the superproject or subproject's (--remote) new tip is so easy, I don't see a need for floating the gitlinks themselves.

Cheers, Trevor

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