Init gist with regular urls via git CLI (http) (#501)

docs/usage/init-via-git.md

@@ -1,6 +1,6 @@
 # Init Gists via Git
 
-Opengist allows you to create new snippets via Git over HTTP.
+Opengist allows you to create new snippets via Git over HTTP. You can create gists with either auto-generated URLs or custom URLs of your choice.
 
 Simply init a new Git repository where your file(s) is/are located:
 
@@ -10,19 +10,41 @@ git add .
 git commit -m "My cool snippet"
 ```
 
-Then add this Opengist special remote URL and push your changes:
+### Option A: Regular URL
+
+Create a gist with a custom URL using the format `http://opengist.url/username/custom-url`, where `username` is your authenticated username and `custom-url` is your desired gist identifier.
+
+The gist must not exist yet if you want to create it, otherwise you will just push to the existing gist.
 
 ```shell
-git remote add origin http://localhost:6157/init
+git remote add origin http://opengist.url/thomas/my-custom-gist
 
 git push -u origin master
 ```
 
-Log in with your Opengist account credentials, and your snippet will be created at the specified URL:
+**Requirements for custom URLs:**
+- The username must match your authenticated username
+- URL format: `http://opengist.url/username/custom-url`
+- The custom URL becomes your gist's identifier and title
+- `.git` suffix is automatically removed if present
+
+### Option B: Init endpoint
+
+Use the special `http://opengist.url/init` endpoint to create a gist with an automatically generated URL:
 
 ```shell
-Username for 'http://localhost:6157': thomas
-Password for 'http://thomas@localhost:6157':
+git remote add origin http://opengist.url/init
+
+git push -u origin master
+```
+
+## Authentication
+
+When you push, you'll be prompted to authenticate:
+
+```shell
+Username for 'http://opengist.url': thomas
+Password for 'http://thomas@opengist.url': [your-password]
 Enumerating objects: 3, done.
 Counting objects: 100% (3/3), done.
 Delta compression using up to 8 threads
@@ -30,12 +52,12 @@ Compressing objects: 100% (2/2), done.
 Writing objects: 100% (3/3), 416 bytes | 416.00 KiB/s, done.
 Total 3 (delta 0), reused 0 (delta 0), pack-reused 0
 remote:
-remote: Your new repository has been created here: http://localhost:6157/thomas/6051e930f140429f9a2f3bb1fa101066
+remote: Your new repository has been created here: http://opengist.url/thomas/6051e930f140429f9a2f3bb1fa101066
 remote:
 remote: If you want to keep working with your gist, you could set the remote URL via:
-remote: git remote set-url origin http://localhost:6157/thomas/6051e930f140429f9a2f3bb1fa101066
+remote: git remote set-url origin http://opengist.url/thomas/6051e930f140429f9a2f3bb1fa101066
 remote:
-To http://localhost:6157/init
+To http://opengist.url/init
  * [new branch]      master -> master
 ```