test annex.shared-sop-command

Test a specified Stateless OpenPGP command with eg:
git-annex test --test-git-config annex.shared-sop-command=sqop

Also documented that config and another one, but so far only the test suite
uses the configs, have not yet implemented using it for actual symmetric
encryption.

Sponsored-by: Joshua Antonishen on Patreon

doc/encryption.mdwn

@@ -76,6 +76,14 @@ The advantage is you don't need to set up gpg keys. The disadvantage is
 that this is **insecure** unless you trust every clone of the git
 repository with access to the encrypted data stored in the special remote.
 
+By default `gpg` is used for shared encryption, but it is also possible to
+use other programs that implement the Stateless OpenPGP command line
+interface. For example, to use Sequoia PGP's `sqop` command, configured to
+be backwards compatable with `gpg`:
+
+    git config annex.shared-sop-command sqop
+    git config annex.shared-sop-profile rfc4880
+
 ## regular public key encryption (encryption=pubkey)
 
 This alternative simply encrypts the files in the special remotes to one or

doc/git-annex-test.mdwn

@@ -44,6 +44,10 @@ framework. Pass --help for details about those.
   One valid use of this is to change a git configuration to a value that
   is planned to be the new default in a future version of git.
 
+  Also, some things can only be tested with a git configuration. For
+  example, annex.shared-sop-command has to be set for the test suite to
+  test using that command.
+
 * `--test-debug`
 
   Normally output of commands run by the test suite is hidden, so even

doc/git-annex.mdwn

@@ -1655,10 +1655,29 @@ Remotes are configured using these settings in `.git/config`.
   precedence over the default GnuPG configuration, which is otherwise
   used.)
 
+* `remote.<name>.annex-shared-sop-command`
+
+  Use this command, which is an implementation of the Stateless OpenPGP
+  command line interface, rather than GnuPG for encrypting and decrypting
+  data. This is only used when a special remote is configured with
+  encryption=shared.
+
+  For example, to use Sequoia PGP's sqop command, set this to "sqop".
+
+* `remote.<name>.annex-shared-sop-profile`
+
+  When encrypting with a Stateless OpenPGP command, this can be used
+  to specify the profile to use, such as "rfc4880".
+
+  For a list of available profiles, run eg "sqop list-profiles encrypt"
+
+  sqop list-profiles encrypt
+
 * `annex.ssh-options`, `annex.rsync-options`,
   `annex.rsync-upload-options`, `annex.rsync-download-options`,
   `annex.bup-split-options`, `annex.gnupg-options`,
-  `annex.gnupg-decrypt-options`
+  `annex.gnupg-decrypt-options`,
+  `annex.shared-sop-command`, `annex.shared-sop-profile`
 
   Default options to use if a remote does not have more specific options
   as described above.