utils/index: add init.defaultBranch= config to git init call

Avoid the following Git warning:

hint: Using 'master' as the name for the initial branch. This default branch name
hint: is subject to change. To configure the initial branch name to use in all
hint: of your new repositories, which will suppress this warning, call:
hint:
hint:   git config --global init.defaultBranch <name>
hint:
hint: Names commonly chosen instead of 'master' are 'main', 'trunk' and
hint: 'development'. The just-created branch can be renamed via this command:
hint:
hint:   git branch -m <name>

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>

utils/index

@@ -17,8 +17,7 @@ project_init() {
 
     mkdir -p $1/data $1/repo
 
-    # This doesn't fail if repo already exists
-    git -C $1/repo init --bare
+    git -C $1/repo -c init.defaultBranch=main init --bare
 
     git config --system --add safe.directory $1/repo
 }