Re: [PATCH 4/5] rebase -i: don't fork git checkout

Hi Phillip,

Le 2021-09-09 à 06:09, Phillip Wood a écrit :

Hi Philippe

On 08/09/2021 19:14, Philippe Blain wrote:

quoted

Hi Phillip,

Le 2021-09-08 à 09:41, Phillip Wood via GitGitGadget a écrit :

quoted

From: Phillip Wood <redacted>

The "apply" based rebase has avoided forking git checkout since ac7f467fef ("builtin/rebase: support running "git rebase
<upstream>"", 2018-08-07). The code that handles the checkout was
moved into libgit by b309a97108 ("reset: extract reset_head()
from rebase", 2020-04-07) so lets start using it for the "merge"
based rebase as well. This opens the way for us to stop calling
the post-checkout hook in the future.

While in general I think it's a good thing to avoid forking, this
change might result in behavioral differences. Any config that
affects 'git checkout' but not the internal 'reset.c::reset_head'
function might play a role in the rebase UX.

One that immediately came to mind is 'submodule.recurse'. This
initial 'onto' checkout was pretty much the only part of 'git
rebase' that did something useful for submodules, so it's kind of
sad to see it regress.

Thanks for pointing that out. As a non-submodule user my question
would be is it actually useful for the initial checkout to work that
way if the rest of rebase (and the checkout for the am backend)
ignores submodules? reset.c::reset_head() just uses unpack trees like
checkout so if rebase read 'submodule.recurse' then reset_head()
would work like 'git checkout' and also 'git rebase --abort' and the
"reset" command in the todo list would start checking out submodules.
I'm reluctant to do that until the merge backend also handles
submodules unless there is a good reason that such partial submodule
support would help submodule users.

Yeah, it's not that useful, I have to admit; it can also be very confusing
since some parts of rebase are affected, and some not. For example, any time
the rebase stops, like for 'edit', 'break', and when there are conflicts, the
submodules are not updated. So I think a full solution is better than a partial
solution; in the meantime I'm thinking the change you are proposing would actually
be less confusing, even if it slightly changes behaviour...

As an aside, I *think* reading submodule.recurse in rebase like it's done in checkout
et al., i.e. something like this:

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 33e0961900..125ec907e4 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c

@@ -26,6 +26,7 @@
 #include "rerere.h"
 #include "branch.h"
 #include "sequencer.h"
+#include "submodule.h"
 #include "rebase-interactive.h"
 #include "reset.h"
 

@@ -1106,6 +1107,9 @@ static int rebase_config(const char *var, const char *value, void *data)
 		return git_config_string(&opts->default_backend, var, value);
 	}
 
+	if (!strcmp(var, "submodule.recurse"))
+		return git_default_submodule_config(var, value, data);
+
 	return git_default_config(var, value, data);
 }
 

would actually also affect the merges
performed during the rebase, since that would affect the "global" state in submodule.c.
I hacked exactly that the other day but did not test extensively...

Cheers,
Philippe.