Git Symlinks in Windows

Creating git symlinks on Windows

UPDATED 2014-11-12 (see below)

git config --global alias.add-symlink '!__git_add_symlink(){
    argv=($@)
    argc=${#argv[@]}

    # Look for options
    options=(" -h")
    o_help="false"
    case "${argv[@]}" in *" -h"*) o_help="true" ;; esac
    if [ "$o_help" == "true" -o "$argc" -lt "2" ]; then
        echo "
Usage: git add-symlink <target> <link>

* <target> is a RELATIVE PATH, respective to <link>.
* <link> is a RELATIVE PATH, respective to the repository'''s root dir.
* Command must be run from the repository'''s root dir."
        return 0
    fi

    target_arg=${argv[0]}
    link_arg=${argv[1]}

    if [ ! -e "$target_arg" ]; then
        echo "ERROR: Target $target_arg does not exist; not creating invalid symlink."
        return 1
    fi

    hash=$(echo -n "$target_arg" | git hash-object -w --stdin)
    git update-index --add --cacheinfo 120000 "$hash" "$link_arg"
    git checkout -- "$link_arg"

}; __git_add_symlink "$@"'

Usage: git add-symlink <src> <dst> , where <src> is a relative reference (with respect to <dst> ) to the current location of the file or directory to link to, and <dst> is a relative reference (with respect to the repository's root) to the link's desired destination.

Eg, the repository tree:

dir/
dir/foo/
dir/foo/bar/
dir/foo/bar/baz      (file containing "I am baz")
dir/foo/bar/lnk_file (symlink to ../../../file)
file                 (file containing "I am file")
lnk_bar              (symlink to dir/foo/bar/)

Can be created on Windows as follows:

git init
mkdir -p dir/foo/bar/
echo "I am baz" > dir/foo/bar/baz
echo "I am file" > file
git add -A
git commit -m "Add files"
git add-symlink ../../../file dir/foo/bar/lnk_file
git add-symlink dir/foo/bar/ lnk_bar
git commit -m "Add symlinks"

Replacing git symlinks with NTFS hardlinks+junctions

git config --global alias.rm-symlink '!__git_rm_symlink(){
    git checkout -- "$1"
    link=$(echo "$1")
    POS=$'''/'''
    DOS=$'''\'''
    doslink=${link//$POS/$DOS}
    dest=$(dirname "$link")/$(cat "$link")
    dosdest=${dest//$POS/$DOS}
    if [ -f "$dest" ]; then
        rm -f "$link"
        cmd //C mklink //H "$doslink" "$dosdest"
    elif [ -d "$dest" ]; then
        rm -f "$link"
        cmd //C mklink //J "$doslink" "$dosdest"
    else
        echo "ERROR: Something went wrong when processing $1 . . ."
        echo "       $dest may not actually exist as a valid target."
    fi
}; __git_rm_symlink "$1"'

git config --global alias.rm-symlinks '!__git_rm_symlinks(){
    for symlink in $(git ls-files -s | egrep "^120000" | cut -f2); do
        git rm-symlink "$symlink"
        git update-index --assume-unchanged "$symlink"
    done
}; __git_rm_symlinks'

Usage:

git rm-symlink dir/foo/bar/lnk_file
git rm-symlink lnk_bar
git update-index --assume-unchanged dir/foo/bar/lnk_file
git update-index --assume-unchanged lnk_bar

This removes git symlinks one-by-one, replacing them with NTFS hardlinks (in the case of files) or NTFS junctions (in the case of directories). The benefit of using hardlinks+junctions over "true" NTFS symlinks is that elevated UAC permissions are not required in order for them to be created. Finally, at your own leisure, you may choose to unflag-as-modified (or not) the "removed" symlinks with git update-index .

For convenience's sake, you can also just run:

git rm-symlinks

This removes ALL git symlinks in the current repository, replacing them with hardlinks+junctions as necessary, and automatically flagging the changes to be ignored by git status .

To remove symlinks from submodules, just use git's built-in support for iterating over them:

git submodule foreach --recursive git rm-symlinks

But, for every drastic action like this, a reversal is nice to have...

Restoring git symlinks on Windows

git config --global alias.checkout-symlinks '!__git_checkout_symlinks(){
    POS=$'''/'''
    DOS=$'''\'''
    for symlink in $(git ls-files -s | egrep "^120000" | cut -f2); do
        git update-index --no-assume-unchanged "$symlink"
        dossymlink=${symlink//$POS/$DOS}
        cmd //C rmdir //Q "$dossymlink" 2>/dev/null
        git  checkout -- "$symlink"
        echo "Restored git symlink $symlink <<===>> $(cat $symlink)"
    done
}; __git_checkout_symlinks'

Usage: git checkout-symlinks , which undoes git rm-symlinks , effectively restoring the repository to its natural state (except for your changes, which should stay intact).

And for submodules:

git submodule foreach --recursive git checkout-symlinks

Limitations:

If people forget to git checkout-symlinks before doing something like git add -A , they could pollute the repo!

Using our "example repo" from before:

echo "I am nuthafile" > dir/foo/bar/nuthafile
echo "Updating file" >> file
git add -A
git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       new file:   dir/foo/bar/nuthafile
#       modified:   file
#       deleted:    lnk_bar           # POLLUTION
#       new file:   lnk_bar/baz       # POLLUTION
#       new file:   lnk_bar/lnk_file  # POLLUTION
#       new file:   lnk_bar/nuthafile # POLLUTION
#

Whoops...

For this reason, it's nice to include these aliases as steps to perform for Windows users before-and-after building a project, rather than after checkout or before pushing. But each situation is different. These aliases have been useful enough for me that a true post-checkout solution hasn't been necessary.