Motivation

Why do I implement this extension, why not use gpg-agent to ask password from user?

The problem is that: when we are working remotely from Windows to Linux, there is no good way to do agent-forward for GPG toolchain.

See also: Git: Support prompting for GPG password · Issue #43809 · microsoft/vscode

To work around this scenario, we launch a fake GPG front-end to ask gpg-agent signing a dummy message, causing it to keep the passphrase in its memory for some period. Thus, following git commit-signing won't cause iterative passphrase-asking process later.

           +-------------+                            +-------------+
           |             |                            |             |
     <-----+ Local Agent |<---x                       |  Fake GPG   |
    Ask    |             | Ask                        |             |
 Passphrase+-------------+                  x         +--+----------+
                                            ^            |
                                    Ask     |            | Sign &
                                 Passphrase |            | Passphrase
                                            |            v
                                         +--+----------------+
                                         |                   |
         +-------+      +-------+        |                   |
  Commit |       | Sign |       |  Sign  |     Agent         |   +--------+
-------->|  GIT  +----->|  GPG  +------->|                   |<--+  key   |
         |       |      |       |        |           +-------+   +--------+
         +-------+      +-------+        |           | pass  |
                                         +-----------+-------+