git submodule add spits unrelated to actual problem error msg about .gitignore

I have spent some time chasing the wild goose (well - the .gitignore file) after getting:

    $> git-submodule add --name fcx-1 ./fcx-1/ ./fcx-1/
    The following path is ignored by one of your .gitignore files:
    fcx-1
    Use -f if you really want to add it.

long story short -- the culprit is this piece of code in git-submodule:

    if test -z "$force" && ! git add --dry-run --ignore-missing "$sm_path" > /dev/null 2>&1
    then
        eval_gettextln "The following path is ignored by one of your .gitignore files:
\$sm_path
Use -f if you really want to add it." >&2
        exit 1
    fi

so if anything goes wrong in git add, it just reports this error message.

FTR -- actual problem in my case was:

    $> git add --dry-run --ignore-missing fcx-1
    fatal: Unable to create '/mnt/datasets/datalad/crawl/crcns/.git/index.lock': File exists.

    Another git process seems to be running in this repository, e.g.
    an editor opened by 'git commit'. Please make sure all processes
    are terminated then try again. If it still fails, a git process
    may have crashed in this repository earlier:
    remove the file manually to continue.

;-)

Cheers! P.S. Please CC me in replies