Add blog post about gitsign cache

Signed-off-by: Daniel Bevenius <daniel.bevenius@gmail.com>

Author: danbev

_posts/2022-12-05-gitsign-cache.md

@@ -0,0 +1,67 @@
+---
+title: "How to Configure a Gitsign Cache"
+date: 2022-12-05
+author: Daniel Bevenius
+---
+
+This post contains the steps for setting up
+[gitsign-credential-cache](https://github.com/sigstore/gitsign/tree/main/cmd/gitsign-credential-cache).
+which is useful if one has to perform multiple commits in short succession, or
+when doing a rebase.
+
+It can be somewhat frustrating to have the browser open for every single
+commit. For these situations a cache can be enabled using the instructions in
+this post.
+
+First install `gitsign-credential-cache` if it is not already installed:
+```console
+$ go install github.com/sigstore/gitsign/cmd/gitsign-credential-cache@latest
+```
+
+Create a file named `~/.config/systemd/user/gitsign.service`:
+```console
+[Unit]
+Description=Gitsign Credentials Cache
+Documentation=https://github.com/sigstore/gitsign
+
+[Service]
+Type=simple
+ExecStart=%h/go/bin/gitsign-credential-cache
+
+Restart=on-failure
+
+[Install]
+WantedBy=default.target 
+```
+This service can then be enabled using:
+```console
+$ systemctl --user daemon-reload
+$ systemctl --user enable gitsign.service 
+Created symlink /home/danielbevenius/.config/systemd/user/default.target.wants/gitsign.service → /home/danielbevenius/.config/systemd/user/gitsign.service.
+```
+And we can start it manually using:
+```console
+$ systemctl --user start gitsign.service
+```
+
+Check that it has started successfully:
+```console
+$ systemctl --user status gitsign.service 
+● gitsign.service - Gitsign Credentials Cache
+     Loaded: loaded (/home/danielbevenius/.config/systemd/user/gitsign.service; enabled; vendor preset: disabled)
+     Active: active (running) since Mon 2022-11-28 11:27:47 CET; 2min 35s ago
+       Docs: https://github.com/sigstore/gitsign
+   Main PID: 177444 (gitsign-credent)
+     CGroup: /user.slice/user-1000.slice/user@1000.service/app.slice/gitsign.service
+             └─ 177444 /home/danielbevenius/go/bin/gitsign-credential-cache
+
+Nov 28 11:27:47 localhost.localdomain systemd[1295]: Started Gitsign Credentials Cache.
+Nov 28 11:27:47 localhost.localdomain gitsign-credential-cache[177444]: /home/danielbevenius/.cache/.sigstore/gitsig>
+```
+And we then need to add the following environment variable:
+```console
+$ export GITSIGN_CREDENTIAL_CACHE=~/.cache/.sigstore/gitsign/cache.sock
+```
+After this we should be able to commit a first time and have our credentials
+stored. Subsequent commits will then be made without a browser "popup".
+