Re: Issue: "Could not access submodule" error when pulling recursively with Git 2.22.0
Hi Gábor,
On Wed, 23 Oct 2019, SZEDER Gábor wrote:
Show 21 quoted lines
> On Wed, Oct 23, 2019 at 07:22:12AM +0000, Aleksey Mikhaylov wrote:
> > "Could not access submodule" error when pulling recursively with Git 2.22.0.
> > This issue causes if there is submodule in submodule.
>
> > Please use my simple test repository to reproduce the problem:
> > https://github.com/agmikhailov/example2361.git
> >
> > It is just an empty repository with one submodule (https://github.com/agmikhailov/example2361M1.git)
> > and one submodule of submodule (https://github.com/agmikhailov/example2361M2.git):
> >
> > git clone https://github.com/agmikhailov/example2361.git
> > cd example2361/
> > git submodule init
>
> According to the docs of 'git submodule init', it "initializes the
> submodules recorded in the index". Therefore, it can only initialize
> the submodule in 'example2361M1', because at this point we have no
> idea that there is a nested submodule in there.
>
> $ git submodule init
> Submodule 'example2361M1' (https://github.com/agmikhailov/example2361M1.git) registered for path 'example2361M1'
Indeed, `git submodule init` is not recursive.
Show 17 quoted lines
> > git submodule update
>
> This command clones 'example2361M1':
>
> $ git submodule update --recursive
> Cloning into '/tmp/example2361/example2361M1'...
> Submodule path 'example2361M1': checked out '6a9be24a1c0ebd44d91ae4dcf1fd62580b936540'
>
> Only at this point can we finally see that there is a nested
> submodule, and can initialize and clone it with:
>
> $ cd example2361M1
> $ git submodule init
> Submodule 'example2361M2' (https://github.com/agmikhailov/example2361M2.git) registered for path 'example2361M2'
> $ git submodule update
> Cloning into '/tmp/example2361/example2361M1/example2361M2'...
> Submodule path 'example2361M2': checked out '9ed39cf1fe0a8cf34e72d2e7ebff1ea9d4a63ac1'
Show 9 quoted lines
> > git pull --recurse-submodules=true
>
> And after that:
>
> $ cd ../..
> $ git pull --recurse-submodules=true
> Fetching submodule example2361M1
> Fetching submodule example2361M1/example2361M2
> Already up to date.
Yes, I agree that _probably_ what the user wanted is to initialize the submodules recursively.
Having said that, I vaguely remember that e.g. Boost has this insane forest of submodules, and I am almost certain that no sane person wants to clone them all. _I_ wouldn't.
Show 29 quoted lines
> > ACTUAL RESULT
> >
> > "git --recurse-submodules=true" command fails with message "Could not access submodule":
> >
> > $ git --recurse-submodules=true
> > Fetching submodule example2361M1
> > Could not access submodule 'example2361M2'
> >
> > EXPECTED RESULT
> >
> > All submodules are successfully updated by "git --recurse-submodules=true" command.
> >
> > ADDITIONAL INFORMATION
> >
> > Git version 2.20.1 does not have this problem.
> > So we had to downgrade Git to work with submodules.
>
> The behavior was indeed different with v2.20.1, but that version
> didn't show the behavior you expected. When running your commands
> with v2.20.1 I get:
>
> $ ~/src/git/bin-wrappers/git pull --recurse-submodules=true
> Fetching submodule example2361M1
> Already up to date.
> $ find example2361M1/example2361M2/
> example2361M1/example2361M2/
>
> So while that 'git pull' didn't error out, it didn't even look at the
> nested submodule, which is still uninitialized and empty.
I would actually argue that this is what is expected: the entire _point_ of submodules is that they can be inactive.
Coming back to the Boost example, what I would want Git to do when only a fraction of the submodules is active is to skip the inactive ones during a `git pull --recurse-submodules=true`.
Which v2.20.1 apparently did, and I would call the current behavior a regression.
> FWIW, bisecting shows that the behavior changed with commit
> a62387b3fc,
Thanks for digging this out!
Show 19 quoted lines
> but, unfortunately, the commit message doesn't seem to be very helpful
> to me, but perhaps others with more experience with submodules can
> make something out of it.
>
> commit a62387b3fc9f5aeeb04a2db278121d33a9caafa7
> Author: Stefan Beller <sbeller@google.com>
> Date: Wed Nov 28 16:27:55 2018 -0800
>
> submodule.c: fetch in submodules git directory instead of in worktree
>
> Keep the properties introduced in 10f5c52656 (submodule: avoid
> auto-discovery in prepare_submodule_repo_env(), 2016-09-01), by fixating
> the git directory of the submodule.
>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
>
> submodule.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
To me, this commit message suggests that the bahvior should not have changed in the reported manner.
Let's look at the diff:
-- snip --
diff --git a/submodule.c b/submodule.c
index 77ace5e784a..d1b6646f42d 100644
--- a/submodule.c
+++ b/submodule.c
@@ -494,6 +494,12 @@ void prepare_submodule_repo_env(struct argv_array *out)
DEFAULT_GIT_DIR_ENVIRONMENT);
}
+static void prepare_submodule_repo_env_in_gitdir(struct argv_array *out)
+{
+ prepare_submodule_repo_env_no_git_dir(out);
+ argv_array_pushf(out, "%s=.", GIT_DIR_ENVIRONMENT);
+}
+
/* Helper function to display the submodule header line prior to the full
* summary output. If it can locate the submodule objects directory it will
* attempt to lookup both the left and right commits and put them into the
@@ -1327,8 +1333,8 @@ static int get_next_submodule(struct child_process *cp,
repo = get_submodule_repo_for(spf->r, submodule);
if (repo) {
child_process_init(cp);
- cp->dir = xstrdup(repo->worktree);
- prepare_submodule_repo_env(&cp->env_array);
+ cp->dir = xstrdup(repo->gitdir);
+ prepare_submodule_repo_env_in_gitdir(&cp->env_array);
cp->git_cmd = 1;
if (!spf->quiet)
strbuf_addf(err, "Fetching submodule %s%s\n",
-- snap --
The obvious difference in behavior is that we no longer let Git
discover the `.git` file/directory, but we define it (because we can).
But actually, we cannot, not if the submodule is not checked out!
Because in this case, there is no `.git` file and Git then tries to
initialize the repository and the worktree, and fails rather miserably
in the reported manner.
Side note: I think there is something spooky going on where we try to
fetch submodules twice when the first time failed, and somehow slip into
the `else` arm of this code:
-- snip --
task->repo = get_submodule_repo_for(spf->r, task->sub);
if (task->repo) {
struct strbuf submodule_prefix = STRBUF_INIT;
child_process_init(cp);
cp->dir = task->repo->gitdir;
prepare_submodule_repo_env_in_gitdir(&cp->env_array);
cp->git_cmd = 1;
if (!spf->quiet)
strbuf_addf(err, "Fetching submodule %s%s\n",
spf->prefix, ce->name);
argv_array_init(&cp->args);
argv_array_pushv(&cp->args, spf->args.argv);
argv_array_push(&cp->args, default_argv);
argv_array_push(&cp->args, "--submodule-prefix");
strbuf_addf(&submodule_prefix, "%s%s/",
spf->prefix,
task->sub->path);
argv_array_push(&cp->args, submodule_prefix.buf);
spf->count++;
*task_cb = task;
strbuf_release(&submodule_prefix);
return 1;
} else {
fetch_task_release(task);
free(task);
/*
* An empty directory is normal,
* the submodule is not initialized
*/
if (S_ISGITLINK(ce->ce_mode) &&
!is_empty_dir(ce->name)) {
spf->result = 1;
strbuf_addf(err,
_("Could not access submodule '%s'"),
ce->name);
}
}
-- snap --
As you can see, at that point, `is_empty_dir()` indicates that it is _no
longer empty_, which means that the recursive pull actually tried to
initialize it, and left things in a half-consistent state.
BTW I also think that Stefan's commit just made a bug very obvious that
had not mattered all that much before: it would seem that before that
commit, when the code tried to fetch a submodule, it would actually
fetch the super project (because it would discover the .git
file/directory, and as the inactive submodule does not have any, it
would have found the super project's).
In essence, I think that the report points out a very real bug, and this
bug should be fixed.
I _could_ imagine that it would be as easy as applying this patch (and
turning the provided reproducer into a regression test), then polishing
this with a nice commit message:
-- snip --
diff --git a/submodule.c b/submodule.c
index 0f199c51378..5694905610a 100644
--- a/submodule.c
+++ b/submodule.c
@@ -1443,6 +1443,12 @@ static int get_next_submodule(struct child_process *cp,
task->repo = get_submodule_repo_for(spf->r, task->sub);
if (task->repo) {
struct strbuf submodule_prefix = STRBUF_INIT;
+
+ /* skip uninitialized submodule */
+ if (!file_exists(task->repo->gitdir) ||
+ is_empty_dir(task->repo->gitdir))
+ continue;
+
child_process_init(cp);
cp->dir = task->repo->gitdir;
prepare_submodule_repo_env_in_gitdir(&cp->env_array);
-- snap --
Any takers?
Ciao,
Johannes
