# Git-annex useful commands

[git-annex][1]

> git-annex allows managing files with git, without checking the file contents into git. While that may seem paradoxical, it is useful when dealing with files larger than git can currently easily handle, whether due to limitations in memory, time, or disk space.

## Getting content

Get all content from `backup` remote:

```shell
git annex get * --from backup
```

## Consistency checks

```shell
time git annex fsck --fast | grep -A 10 -v "ok$"

time git annex fsck | grep -A 10 -v "ok$"
```

## Find non-distributed content

```shell
git annex find --not --in=<remote> .
```

## Disk space usage

Check how much disk space the content from `backup` remote will use when fetched:

```shell
git annex info . --not --in here
```

## Migrate to different backend

To migrate from older SHA1E backend to newer SHA256E (default for new repos):

```shell
git annex migrate --backend SHA256E *
```

After migration you might need to run `git annex unused` and `git annex dropunused`.

```shell
git annex unused

git annex unused | grep -o -P "^    [0-9]+" | xargs git annex dropunused
```

If there are still files in a specific backend:

```console
$ git annex info
...
backend usage: 
	SHA1E: 29
	SHA256E: 973
```

Show which remotes contain files with `backend=SHA1E`:

```console
$ git annex list --inbackend=SHA1E
here
|backup
||github
|||origin
||||web
|||||bittorrent
||||||
_X____ foobar1.txt
...
```

## Purging dead repositories

```shell
git annex dead <UUID>
```

To prune all history relating to all dead remotes

```shell
git annex forget --drop-dead
```

> That prunes all history relating to all dead remotes. You need to be running a git-annex that supports this on all computers you use the repos on, or the pruned history will get merged back in.
 
## Recycle dead repo UUIDs

First clone the repo to new location:

```shell
git clone foo
```

Now set "annex.uuid" in freshly created `.git/config` to the UUID of the dead repo you want to recycle.
Do this _before_ you run any git annex command. Now run:

```shell
git annex init
git annex fsck
git annex semitrust <uuid>
```

Sync with master.

## Automatically adding metadata

Git-annex's metadata works best when files have a lot of useful metadata attached to them.
To make git-annex automatically set the year and month when adding files, run:

```shell
git config annex.genmetadata true
```

A git commit hook can be set up to extract lots of metadata from files like photos, mp3s, etc. Install the extract utility, from [libextractor][2].

Download pre-commit-annex and install it in your git-annex repository as '.git/hooks/pre-commit-annex'.
Remember to make the script executable! Run:

```shell
git config metadata.extract "artist album title camera_make camera_model orientation video_dimensions image_dimensions"
```

Running for first time to update already annexed content:

```shell
git annex find --format='${file}\n' | sort | \
    awk -vRS= -vFS='\n' '{for (i = 2; i <= NF; i++) print $i}' | \
    xargs -d '\n' bash -x .git/hooks/pre-commit-annex
```

Now any fields you list in metadata.extract to will be extracted and stored when files are committed.

To get a list of all possible fields, run:

```shell
libextractor-extract -L | sed 's/ /_/g'
```

By default, if a git-annex already has a metadata field for a file, its value will not be overwritten with metadata taken from files. To allow overwriting, run:

```shell
git config metadata.overwrite true
```

---

**Links**

* [git-annex][1]
* [libextractor][2]

[//]: # (invisible, for link references)
[1]: https://git-annex.branchable.com
[2]: http://www.gnu.org/software/libextractor