git-lfs Migration Cheatsheet

git-lfs-migration-cheatsheet

Guide to Fixing LFS Tracking on Repos

Prereqs: 
git version >= 2.3 
git-lfs version >= 2.3 
OSX: homebrew 
OSX: coreutils  - once you have homebrew installed, run > brew install coreutils 

(note to self: use the fastest way, see bottom-ish of doc!)

INVESTIGATION

As a basic first step, you can run: 
> git lfs migrate info --everything 
which will give a list of the top 5 file types that are taking up space in the repo. 
The "--everything" means it will look across all branches.

for even more info:
git lfs migrate info --everything --top=25
This will give an additional 25 file types

If you want to get a sense of the actualy files that are taking up space, 
this command will get you a list of the biggest files in the repo.
It can be very useful for finding extension-less files, like those
inside .app files on OSX, etc.:

> git rev-list --objects --all \
| git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' \
| sed -n 's/^blob //p' \
| sort --numeric-sort --key=2 \
| cut -c 1-12,41- \
| $(command -v gnumfmt || echo numfmt) --field=2 --to=iec-i --suffix=B --padding=7 --round=nearest

and this one will filter that list against files already tracked in lfs, so you only see the non-tracked files: 

> git rev-list --objects --all \
| git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' \
| sed -n 's/^blob //p' \
| grep -vF --file=<(git lfs ls-files -a | awk '{print $3}') \
| sort --numeric-sort --key=2 \
| cut -c 1-12,41- \
| $(command -v gnumfmt || echo numfmt) --field=2 --to=iec-i --suffix=B --padding=7 --round=nearest


MIGRATION

If you already had a .gitattributes file in your repo from the first commit, and it has all the types you want to lfs, you can run
> git lfs migrate import --everything --fixup
and that should move all those files to LFS

If your .gitattributes wasn't started with the repo, or doesn't include all the types you want, you can start running one-off commands:
> git lfs migrate info --everything --include="*.psd" 
    this will preview the migration

> git lfs migrate import --everything --include="*.psd"
    this will actually run it

Note that you can do multiple files types at the same time
> git lfs migrate import --everything --include="*.psd,*.bmp"

Remember you can omit --everything if you're only trying to clean up a single branch

Look here to see if there have been any updates to make it possible to specifiy the .gitattributes file you want to use
when calling lfs migrate: https://github.com/git-lfs/git-lfs/issues/3442 

FASTEST WAY BUT SCARY

If you're feeling ambitious, you could try putting the .gitattributes in the first commit by rewriting history.
For this to work, you need a .gitattributes in your git repo that has all the lfs types you want spec'd.

Then it's just a matter of re-writing the first commit (and therefore the whole tree), placing the .gitattributes file in
the first commit:
> git filter-branch --index-filter 'cd ../..;git update-index --add .gitattributes;cd -' -- --all

Then running fixup across all the branches
> git lfs migrate import --everything


FLOW

Usually, if I don't have a .gitattributes set up already, I would end up running something like:
> git lfs migrate info --everything --include="*.psd,*.bpm...etc" 
> git lfs migrate import --everything --include="*.psd,*.bpm...etc" 
> git gc 
over and over until it's reporting as expected.

For a Unity project, I expect something like:

*.meta  	34 MB 	27869/27869 files(s)	100%
*.mat   	20 MB 	  8461/8461 files(s)	100%
*.cs    	18 MB 	  1869/1872 files(s)	100%
*.html  	1.4 MB	      39/39 files(s)	100%
*.shader	1.4 MB	    311/311 files(s)	100%

FINAL STEPS

Run garbage collector locally:
> git gc

Run this command to push all those changes to the remote repo
> git push --all -f 

You can omit --all if you are only working on one branch