git source element uses inconsistent remote names and cannot update local repo

Summary

In some configurations, the git source element uses different remote names when cloning a repository and when trying to update the local repository later. I was able to reproduce this only when there is a mirror configured on the same HTTP host as the canonical URL.

Steps to reproduce

1. Start an HTTP server serving static files from some directory you can write to.

2. Define shell variables $http_dir as the directory served over HTTP, and $http_url as its HTTP URL.

3. In a temporary directory, run the following commands.

cat >project.conf <<EOT
name: build
element-path: .
aliases:
  local: $http_url
mirrors:
- name: my_mirror
  aliases:
    local:
    - $http_url/fake-mirror/
EOT

git init $http_dir/upstream
(cd $http_dir/upstream && echo foo > foo && git add foo && git commit -m foo)
GIT_DIR=$http_dir/upstream/.git git update-server-info

upstream_ref=$(GIT_DIR=$http_dir/upstream/.git git rev-parse HEAD)
cat >upstream.bst <<EOT
kind: import
sources:
- kind: git
  url: local:upstream/.git
  ref: $upstream_ref
config:
  target: /
EOT
bst build upstream.bst

(cd $http_dir/upstream && echo bar > foo && git add foo && git commit -m bar)
GIT_DIR=$http_dir/upstream/.git git update-server-info

new_upstream_ref=$(GIT_DIR=$http_dir/upstream/.git git rev-parse HEAD)
sed -i "s/$upstream_ref/$new_upstream_ref/" upstream.bst
bst build upstream.bst

What is the current bug behavior?

The second build fails, with error messages like:

    Running host command /home/bwh/.cache/buildstream/sources/git/local_upstream__git: /usr/bin/git fetch http___192_168_122_1__bwh_bst_test_ --prune --force --tags
    [--:--:--] STATUS  upstream.bst-0: Running host command

        /usr/bin/git fetch http___192_168_122_1__bwh_bst_test_ --prune --force --tags
    fatal: 'http___192_168_122_1__bwh_bst_test_' does not appear to be a git repository
    fatal: Could not read from remote repository.

The repository in /home/bwh/.cache/buildstream/sources/git/local_upstream__git only has the remotes:

http___192_168_122_1__bwh_bst_test__fake_mirror_
origin

What is the expected correct behavior?

Either the first build should have created the local repo with a remote named after the canonical URL, or the second build should fetch from the origin remote.

Relevant logs and/or screenshots

Possible fixes

Other relevant information

• BuildStream version affected: /milestone %BuildStream_v1.4

I'm running BuildStream 1.4.3 and have not tested the master branch.

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