bug(forgejo): Improved auto-detection

Previously, the Forgejo/Gitea auto-detection worked by hittin an
endpoint that only exists on these forges, out of the ones we support.
But it had no indication other than its existence that it is a Forgejo
instance.

While looking at other ways to identify these, I found the
`/swagger.v1.json` endpoint. It has the full API documentation in a
Swagger JSON format, and includes an `info.title` key, which *does*
mention "Gitea API" or "Forgejo API", depending on the forge. It's a
rather large document, however.

Luckily, we don't need the whole document! This file is part of the web
UI, not the API itself, and as such, includes cookies! One of those
cookies is `i_like_gitea` (for both Forgejo and Gitea). As such, we can
do a HEAD request, and check the cookie.

This is both more reliable than the old method, and involves less
network traffic too.

Signed-off-by: Gergely Nagy <me@gergo.csillger.hu>

Cargo.toml

@@ -24,7 +24,7 @@ hyper = { version = "0.14.27", features = ["client"] }
 log = "0.4.20"
 pretty_env_logger = "0.5.0"
 regex = "1.10.2"
-reqwest = { version = "0.11.22", features = ["json"] }
+reqwest = { version = "0.11.22", features = ["cookies", "json"] }
 serde = { version = "1.0.190", features = ["derive"] }
 serde_json = "1.0.107"
 serde_yaml = "0.9.27"

src/api/v1/forges/forgejo.rs

@@ -25,17 +25,17 @@ impl Forgejo {
     }
 
     pub async fn is_host_forgejo(host: &str) -> Result<bool, ForgeError> {
-        // I couldn't find a more reasonable way to detect Forgejo, so we'll check
-        // an API endpoint that is specific to this forge, and if it exists, we
-        // assume it's a Forgejo instance.
-        let uri = format!("https://{}/api/v1/settings/api", &host);
-        let client = reqwest::Client::builder().user_agent(USER_AGENT).build()?;
+        let uri = format!("https://{}/swagger.v1.json", &host);
+        let client = reqwest::Client::builder()
+            .user_agent(USER_AGENT)
+            .cookie_store(true)
+            .build()?;
         let res = client
-            .get(&uri)
+            .head(uri)
             .header(ACCEPT, "application/json")
             .send()
             .await?;
-        Ok(res.status() == 200)
+        Ok(res.status() == 200 && res.cookies().any(|cookie| cookie.name() == "i_like_gitea"))
     }
 }