The termux Android app includes git-annex in its package repository, so installation is easy:

pkg install git-annex

Starting git-annex assistant

Just run "git-annex webapp" inside Termux. A browser window will open with the git-annex interface.

?webapp.png

Closing and reopening the webapp

The webapp does not need to be left open after you've set up your repository. As long as Termux is left open, git-annex will remain running and sync your files.

Starting at power on

If you install the Termux:Boot app, git-annex will be automatically started when your Android device powers on. It will run in the background in whatever repositories you have set up in the webapp.

Using the command line

If you prefer to use git-annex at the command line, you can do so inside Termux. Here we'll make a repository for photos:

    cd ~/storage/dcim
    git init
    git-annex init

You can go on to set up a ssh remote pointing to a server, and sync your files to and from it.

And so on. Most ways you would use git-annex on a Linux system work fairly well in the Termux environment.

Upgrading

To upgrade to a new git-annex release, just run git-annex-install again.