getting remote name and ref from local ref

git-find-ref

#!/bin/bash

# git find-ref $committish
#
# figure out which remote a committish comes from, and open its
# corresponding web view in a browser
#
# NOTE: doesn't work with tag names, I'm not sure if it's possible to
# know where a tag comes from

# default to HEAD
rev="${1:-HEAD}"
# resolve the committisg to a branch name, plus possibly some parent
# information (e.g. `master`, `origin/master`, `origin/master~3`
ref="$(git name-rev --exclude='refs/tags/*' --name-only --no-undefined "$rev" 2>/dev/null )"
# default to master if we can't identify
: ${ref:=master}

# did we get a remote ref?
if [[ "$ref" == remotes/* ]]; then
    ref="refs/$ref"
    # scan all remotes (the `IFS` is to make sure we support remotes
    # with spaces in their names, the `while ... done < <(foo)` is
    # because `foo|while ... done` runs the `while` in a sub-shell and
    # wouldn't update our variables)
    while IFS=$'\n' read o; do
        # this will produce something like
        # `+refs/heads/*:refs/remotes/origin/*`
        fetch="$(git config "remote.$o.fetch")"
        fetch="${fetch#*:}"
        # == does pattern matching
        if [[ $ref == $fetch ]]; then
            remote="$o"
            # remove matching prefix, the `*` at the end will not eat
            # anything because `#` removes the *shortest* matching
            # prefix
            ref="${ref#$fetch}"
            break
        fi
    done < <(git remote)
else
    # not an explicitly remote ref, let's get its remote from its
    # tracking information
    remote="$(git config --get "branch.${ref}.remote")"
    : ${remote:=origin}
    # and the remote branch name as well
    merge_branch="$(git config --get "branch.${ref}.merge")"
    merge_branch=${merge_branch#refs/heads/}
    # if there's no merge branch, assume it's the same as the name we
    # already got
    ref="${merge_branch:-$ref}"
fi

remote_url="$(git remote get-url "$remote")"
: ${remote_url:="$(git remote get-url --push "$remote")"}

echo "ref=[${ref}]"
echo "remote=[${remote}]"
echo "remote_url=[${remote_url}]"