Porting git-annex to Android will use the Android native SDK.

A hopefully small Java app will be developed, which runs the webapp
daemon, and a web browser to display it.

[[!toc]]

### programs to port

These will probably need to be bundled into the Android app, unless already
available in the App Store.

* ssh (native ssh needed for scp, not a client like ConnectBot)
* rsync
* gpg
* git (not all git commands are needed,
  but core plumbing and a few like `git-add` are.)

### FAT sucks

The main media partition will use some awful FAT filesystem format from
1982 that cannot support git-annex's symlinks. (Hopefully it can at least
handle all of git's filenames.) Possible approaches to this follow.

(May want to consider which of these would make a Windows port easier too.)

#### bare git repo with file browser

Keep only a bare git repo on Android. The app would then need to include
a file browser to access the files in there, and adding a file would move
it into the repo. 

Not ideal.

#### implement git smudge filters

See [[smudge]].

Difficult. Would make git-annex generally better.

#### keep files outside bare git repo

Use a bare git repo but don't keep files in `annex/objects`, instead
leave them outside the repo, and add some local mapping to find them.

Problem: Would leave files unlocked to modification, which might lose a
version git-annex dependend upon existing on the phone. (Maybe the phone
would have to be always considered an untrusted repo, which probably
makes sense anyway.)

Problem: 

#### crazy `LD_PRELOAD` wrapper

Need I say more? (Also, Android's linker may not even support it.)

### partial content

On a regular system, a reasonable simplifying assumption is that all the
files in the folder will be synced to the system. A user might want to
disable syncing of some subdirectories, for eg, archived files. But in
general, things are simpler to understand and implement if all files sync.

But, a phone probably cannot hold all a user's files. Indeed, it's likely
that old files will be aggressively dropped from the phone after syncing to
elsewhere, in order to keep enough free space on it for new files. 

There needs to be a way for the user to browse files not on the phone and
request they be transferred to it. This could be done as a browser in the
web app, or using a subdirectory full of placeholder files (not symlinks;
see above) that start transfer of the real file when accessed.