This bash script will transform a relative or absolute path to file or dir into a github URL you can browse and share.

git_path_to_github_url.sh

#!/bin/bash

# Transform a relative or absolute path to file or dir into a github URL you can browse and share.
#
# usage: git_path_to_github_url.sh -
# usage: git_path_to_github_url.sh somedir/somefile

for ENTRY
do
    (
        FULLPATH=$([[ "$ENTRY" = /* ]] && echo "$ENTRY" || echo "$PWD/${ENTRY#./}")
        cd "${FULLPATH%/*}/"
        GITROOT="$( git rev-parse --show-toplevel )"
        BRANCH="$( git rev-parse --abbrev-ref HEAD )"

        if [[ "$ENTRY" == "-" ]]
        then
            RELPATH=""
            KIND=tree
        else
            RELPATH="${FULLPATH/$GITROOT\//}"
            if [[ -f "$FULLPATH" ]] ; then KIND=blob ; fi
            if [[ -d "$FULLPATH" ]] ; then KIND=tree ; fi
        fi

        if [[ -z "$KIND" ]]
        then
            echo >&2 "Cannot figure out URL (does it even exist?): $FULLPATH"
            continue
        fi

        while read -u 3 REMOTENAME REMOTEPATH
        do
            echo $REMOTEPATH/$KIND/$BRANCH/$RELPATH
        done 3< <( git remote -v show | cut -f 1 -d " " | sort | uniq )
    )
done | sed 's|^[^ ]*github.com:/*|https://github.com/|'