[PATCHv3 1/5] submodule: prepare recursive path from non root directory

[Stefan Beller <sbeller@google.com>]

One of the first things that happens in most submodule sub commands is

    git submodule--helper list --prefix "$wt_prefix"

Currently the passed --prefix is used for doing path calculation
as if we were in that path relative to the repository root, which is
why we need to pass "$wt_prefix". A more common way in Git however
would be to use

    git -C "$wt_prefix" submodule--helper list

which I want to change to later as it is easier to understand for
readers of the code base. That way however does not just pass the
prefix into the submodule command, but also changes into that
directory. Say you have the following setup:

    repo/ # a superproject repository
    repo/untracked/ # an untracked dir in repo/
    repo/sub/ # a submodule
    repo/sub/subsub # a submodule of a submodule

When in repo/untracked/ and invoking "git submodule status --recursive",
the recursed instance of the latter version for listing submodules would
try to change into the directory repo/sub/untracked, which is a bug.
This happens as we cd into the submodule in git-submodule.sh without
clearing wt_prefix, which is the assumed relative path inside the working
directory.

Most times that directory doesn't exist and we error out. Fix this potential
bug by clearing wt_prefix, such that any recursive instances of will assume
to operate from the root of the respective submodule.

When changing wt_prefix, we need to make sure the reported paths stay
correct, as paths are reported relative to the wt_prefix. We can fix
this by computing the relative path before changing the wt_prefix.

As we do not pass in filenames or pathspecs into submodules recursively,
we do not need to care about filenames being relative to wt_prefix,
so fixing the display path for error reporting is the only thing we
need to do.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 git-submodule.sh | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/git-submodule.sh b/git-submodule.sh
index 43c68de..d83608c 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -825,8 +825,9 @@ Maybe you want to use 'update --init'?")"
 		if test -n "$recursive"
 		then
 			(
-				prefix="$prefix$sm_path/"
+				prefix="$(relative_path $prefix$sm_path)/"
 				clear_local_git_env
+				wt_prefix=
 				cd "$sm_path" &&
 				eval cmd_update
 			)
@@ -1159,6 +1160,7 @@ cmd_status()
 			(
 				prefix="$displaypath/"
 				clear_local_git_env
+				wt_prefix=
 				cd "$sm_path" &&
 				eval cmd_status
 			) ||
@@ -1239,7 +1241,8 @@ cmd_sync()
 
 				if test -n "$recursive"
 				then
-					prefix="$prefix$sm_path/"
+					prefix=$(relative_path "$prefix$sm_path/")
+					wt_prefix=
 					eval cmd_sync
 				fi
 			)
-- 
2.8.0.rc4.10.g52f3f33.dirty