Git Symlinks in Windows

Question

I was asking this exact same question a while back (not here, just in general) and ended up coming up with a very similar solution to OP's proposition. First I'll provide direct answers to questions 1 2 & 3, and then I'll post the solution I ended up using.

1. There are indeed a few downsides to the proposed solution, mainly regarding an increased potential for repository pollution, or accidentally adding duplicate files while they're in their "Windows symlink" states. (More on this under "limitations" below.)
2. Yes, a post-checkout script is implementable! Maybe not as a literal post-git checkout step, but the solution below has met my needs well enough that a literal post-checkout script wasn't necessary.
3. Yes!

The Solution:

Our developers are in much the same situation as OP's: a mixture of Windows and Unix-like hosts, repositories and submodules with many git symlinks, and no native support (yet) in the release version of MsysGit for intelligently handling these symlinks on Windows hosts.

Thanks to Josh Lee for pointing out the fact that git commits symlinks with special filemode 120000. With this information it's possible to add a few git aliases that allow for the creation and manipulation of git symlinks on Windows hosts.

1. Creating git symlinks on Windows

   git config --global alias.add-symlink '!'"$(cat <<'ETX'
   __git_add_symlink() {
     if [ $# -ne 2 ] || [ "$1" = "-h" ]; then
       printf '%b\n' \
           'usage: git add-symlink <source_file_or_dir> <target_symlink>\n' \
           'Create a symlink in a git repository on a Windows host.\n' \
           'Note: source MUST be a path relative to the location of target'
       [ "$1" = "-h" ] && return 0 || return 2
     fi
   
     source_file_or_dir=${1#./}
     source_file_or_dir=${source_file_or_dir%/}
   
     target_symlink=${2#./}
     target_symlink=${target_symlink%/}
     target_symlink="${GIT_PREFIX}${target_symlink}"
     target_symlink=${target_symlink%/.}
     : "${target_symlink:=.}"
   
     if [ -d "$target_symlink" ]; then
       target_symlink="${target_symlink%/}/${source_file_or_dir##*/}"
     fi
   
     case "$target_symlink" in
       (*/*) target_dir=${target_symlink%/*} ;;
       (*) target_dir=$GIT_PREFIX ;;
     esac
   
     target_dir=$(cd "$target_dir" && pwd)
   
     if [ ! -e "${target_dir}/${source_file_or_dir}" ]; then
       printf 'error: git-add-symlink: %s: No such file or directory\n' \
           "${target_dir}/${source_file_or_dir}" >&2
       printf '(Source MUST be a path relative to the location of target!)\n' >&2
       return 2
     fi
   
     git update-index --add --cacheinfo 120000 \
         "$(printf '%s' "$source_file_or_dir" | git hash-object -w --stdin)" \
         "${target_symlink}" \
       && git checkout -- "$target_symlink" \
       && printf '%s -> %s\n' "${target_symlink#$GIT_PREFIX}" "$source_file_or_dir" \
       || return $?
   }
   __git_add_symlink
   ETX
   )"
   

   Usage: git add-symlink <source_file_or_dir> <target_symlink>, where the argument corresponding to the source file or directory must take the form of a path relative to the target symlink. You can use this alias the same way you would normally use ln.

   E.g., 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"
   

2. Replacing git symlinks with NTFS hardlinks+junctions

   git config --global alias.rm-symlinks '!'"$(cat <<'ETX'
   __git_rm_symlinks() {
     case "$1" in (-h)
       printf 'usage: git rm-symlinks [symlink] [symlink] [...]\n'
       return 0
     esac
     ppid=$$
     case $# in
       (0) git ls-files -s | grep -E '^120000' | cut -f2 ;;
       (*) printf '%s\n' "$@" ;;
     esac | while IFS= read -r symlink; do
       case "$symlink" in
         (*/*) symdir=${symlink%/*} ;;
         (*) symdir=. ;;
       esac
   
       git checkout -- "$symlink"
       src="${symdir}/$(cat "$symlink")"
   
       posix_to_dos_sed='s_^/\([A-Za-z]\)_\1:_;s_/_\\\\_g'
       doslnk=$(printf '%s\n' "$symlink" | sed "$posix_to_dos_sed")
       dossrc=$(printf '%s\n' "$src" | sed "$posix_to_dos_sed")
   
       if [ -f "$src" ]; then
         rm -f "$symlink"
         cmd //C mklink //H "$doslnk" "$dossrc"
       elif [ -d "$src" ]; then
         rm -f "$symlink"
         cmd //C mklink //J "$doslnk" "$dossrc"
       else
         printf 'error: git-rm-symlink: Not a valid source\n' >&2
         printf '%s =/=> %s  (%s =/=> %s)...\n' \
             "$symlink" "$src" "$doslnk" "$dossrc" >&2
         false
       fi || printf 'ESC[%d]: %d\n' "$ppid" "$?"
   
       git update-index --assume-unchanged "$symlink"
     done | awk '
       BEGIN { status_code = 0 }
       /^ESC\['"$ppid"'\]: / { status_code = $2 ; next }
       { print }
       END { exit status_code }
     '
   }
   __git_rm_symlinks
   ETX
   )"
   
   git config --global alias.rm-symlink '!git rm-symlinks'  # for back-compat.
   

   Usage:

   git rm-symlinks [symlink] [symlink] [...]
   

   This alias can remove git symlinks one-by-one or all-at-once in one fell swoop. Symlinks will be replaced 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.

   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...

3. Restoring git symlinks on Windows

   git config --global alias.checkout-symlinks '!'"$(cat <<'ETX'
   __git_checkout_symlinks() {
     case "$1" in (-h)
       printf 'usage: git checkout-symlinks [symlink] [symlink] [...]\n'
       return 0
     esac
     case $# in
       (0) git ls-files -s | grep -E '^120000' | cut -f2 ;;
       (*) printf '%s\n' "$@" ;;
     esac | while IFS= read -r symlink; do
       git update-index --no-assume-unchanged "$symlink"
       rmdir "$symlink" >/dev/null 2>&1
       git checkout -- "$symlink"
       printf 'Restored git symlink: %s -> %s\n' "$symlink" "$(cat "$symlink")"
     done
   }
   __git_checkout_symlinks
   ETX
   )"
   
   git config --global alias.co-symlinks '!git checkout-symlinks'
   

   Usage: git checkout-symlinks [symlink] [symlink] [...], 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
   

4. Limitations:

   • Directories/files/symlinks with spaces in their paths should work. But tabs or newlines? YMMV… (By this I mean: don’t do that, because it will not work.)

   • If yourself or others forget to git checkout-symlinks before doing something with potentially wide-sweeping consequences like git add -A, the local repository could end up in a polluted state.

     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.

Hope that helps!

References:

http://git-scm.com/book/en/Git-Internals-Git-Objects

http://technet.microsoft.com/en-us/library/cc753194

Last Update: 2019-03-13

• POSIX compliance (well, except for those mklink calls, of course) — no more Bashisms!
• Directories and files with spaces in them are supported.
• Zero and non-zero exit status codes (for communicating success/failure of the requested command, respectively) are now properly preserved/returned.
• The add-symlink alias now works more like ln(1) and can be used from any directory in the repository, not just the repository’s root directory.
• The rm-symlink alias (singular) has been superseded by the rm-symlinks alias (plural), which now accepts multiple arguments (or no arguments at all, which finds all of the symlinks throughout the repository, as before) for selectively transforming git symlinks into NTFS hardlinks+junctions.
• The checkout-symlinks alias has also been updated to accept multiple arguments (or none at all, == everything) for selective reversal of the aforementioned transformations.

Final Note: While I did test loading and running these aliases using Bash 3.2 (and even 3.1) for those who may still be stuck on such ancient versions for any number of reasons, be aware that versions as old as these are notorious for their parser bugs. If you experience issues while trying to install any of these aliases, the first thing you should look into is upgrading your shell (for Bash, check the version with CTRL+X, CTRL+V). Alternatively, if you’re trying to install them by pasting them into your terminal emulator, you may have more luck pasting them into a file and sourcing it instead, e.g. as

. ./git-win-symlinks.sh

Good luck!

You can find the symlinks by looking for files that have a mode of 120000, possibly with this command:

git ls-files -s | awk '/120000/{print $4}'

Once you replace the links, I would recommend marking them as unchanged with git update-index --assume-unchanged, rather than listing them in .git/info/exclude.

The most recent version of git scm (testet 2.11.1) allows to enable symbolic links. But you have to clone the repository with the symlinks again git clone -c core.symlinks=true <URL>. You need to run this command with administrator rights. It is also possible to create symlinks on Windows with mklink. Check out the wiki.

2020/2021 TL;DR Answer

1. Enable "Developer Mode" in Windows 10/11 -- gives mklink permissions
2. Ensure symlinks are enabled in git
   • git config --global core.symlinks true
   • or
   • check the checkbox when installing msysgit

Switching branches will force the recreation of missing symlinks.

Be careful, support for Symlinks in git on Windows is relatively new. There are some bugs that still affect some git clients. Notably, symlinks with relative (..) paths are mangled in some programs because of a (fixed) regression in libgit2. For instance, GitKraken is affected by this because they are waiting on nodegit to update libgit2 from v0.x to v1.x, which includes the fix.

so as things have changed with GIT since alot of these answers were posted here is the correct instructions to get symlinks working correctly in windows as of

AUGUST 2018

---

1. Make sure git is installed with symlink support

2. Tell Bash to create hardlinks instead of symlinks

EDIT -- (git folder)/etc/bash.bashrc

ADD TO BOTTOM - MSYS=winsymlinks:nativestrict

3. Set git config to use symlinks

git config core.symlinks true

or

git clone -c core.symlinks=true <URL>

NOTE: I have tried adding this to the global git config and at the moment it is not working for me so I recommend adding this to each repo...

4. pull the repo

NOTE: Unless you have enabled developer mode in the latest version of Windows 10, you need to run bash as administrator to create symlinks

5. Reset all Symlinks (optional) If you have an existing repo, or are using submodules you may find that the symlinks are not being created correctly so to refresh all the symlinks in the repo you can run these commands.

find -type l -delete
git reset --hard

NOTE: this will reset any changes since last commit so make sure you have committed first

It ought to be implemented in msysgit, but there are two downsides:

• Symbolic links are only available in Windows Vista and later (should not be an issue in 2011, and yet it is...), since older versions only support directory junctions.
• (the big one) Microsoft considers symbolic links a security risk and so only administrators can create them by default. You'll need to elevate privileges of the git process or use fstool to change this behavior on every machine you work on.

I did a quick search and there is work being actively done on this, see issue 224.