Jay Soffian <jaysoff...@gmail.com> writes:
> Teach "git submodule foreach" a --revision <tree-ish> option. This
> is useful in combination with $sha1 to perform git commands that
> take a revision argument.
The above says:
- "--revision T" is added.
OK. There is no information whatsoever what it does to convince
us why it is useful.
- This is useful.
Huh? How can anybody supposed to agree or disagree with that
claim, when nothing is said about what it does in the first
place?
> For example:
>
> $ git submodule foreach --revision v1.0 'git tag v1.0 $sha1'
Whose "v1.0" does this example refer to?
The first line of the proposed log message says it is <tree-ish>,
which means that you can safely substitute "--revision T" with
"--revision $(git rev-parse T^{tree}), so it must name a concrete
single object that is a tree (not a tree-ish). In which repository
is that object found? The top-level superproject? All submodule
repositories share the same object store with the superproject?
The description doesn't make _any_ sense to me. The feature might be
something worth considering about with a better description, but
with the above, I can't tell if it is.
> + If `--revision <tree-ish>` is given, submodules are traversed starting
> + at the given <tree-ish>.
What does "are traversed starting at the given <tree-ish>"? The
desired or expected state of each submodule is recorded as a commit
object name (not even commit-ish) in its superproject. Did you mean
"commit-ish"?
> + Though this does not alter the submodule check
> + outs, it may be combined with $sha1 to perform git commands that can
> + operate on a particular commit, such as linkgit:git-tag[1].
Here is what I am guessing, partially with help from the horrible example:
> $ git submodule foreach --revision v1.0 'git tag v1.0 $sha1'
>
> Previously, this would have required multiple steps:
>
> $ git checkout v1.0
> $ git submodule update
> $ git submodule foreach 'git tag v1.0'
where there appears two v1.0 that are used for totally different
purposes which does not help guessing. Perhaps "--revision" names a
tree-ish taken from the top-level superproject, and for each
submodule that appear in the tree in the superproject, the command
specified by foreach is run with the usual $sha1, $name, $path set
to the state in the submodules that top-level tree wants to have,
and this is done without actually checking anything out. So the
first v1.0 in that confusing example is about specifying a tree in
the superproject repository, and the second v1.0 does not have any
relationship with that first v1.0 (the first one could have been HEAD~2
when you have committed twice in the superproject since you tagged v1.0
and remembered that you forgot to tag its submodules).
Assuming that the above guess is correct (which is a huge
assumption, given the lack of clarity in the description), I think
the feature might make sense. The example would have been a lot
easier to follow if it were something like this:
$ git submodule foreach --revision v1.0 'git grep -e frotz $sha1'
> @@ -379,6 +379,7 @@ Use -f if you really want to add it." >&2
> cmd_foreach()
> {
> # parse $args after "submodule ... foreach".
> + revision=
> while test $# -ne 0
> do
> case "$1" in
> @@ -388,6 +389,11 @@ cmd_foreach()
> --recursive)
> recursive=1
> ;;
> + --revision)
> + git rev-parse --quiet --verify "$2" >/dev/null || usage
> + revision=$2
Shouldn't this part of the code verify $2^{tree} instead to ensure
that "$2" is a tree-ish?
> + shift
> + ;;
> -*)
> usage
> ;;
> @@ -404,7 +410,17 @@ cmd_foreach()
> # command in the subshell (and a recursive call to this function)
> exec 3<&0
>
> - module_list |
> + if test -n "$revision"
> + then
> + # make ls-tree output look like ls-files output
> + git ls-tree -r $revision | grep '^160000 ' |
> + while read mode unused sha1 sm_path
> + do
> + echo "$mode $sha1 0 $sm_path"
> + done
> + else
> + module_list
> + fi |
Hrm, it is somewhat unfortunate that you cannot limit the set of
submodules to apply foreach to, like other commands like init,
update, status, etc. (not a new problem).
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