rhg: Fall back to Python on --repository with an URL

A low-hanging fruit to improve on this would be to properly parse
and handle `file:` URLs. But other Python-based hg supports
some other URL schemes for features that rhg does not support yet.

Differential Revision: https://phab.mercurial-scm.org/D10101

rust/Cargo.lock

@@ -826,8 +826,10 b' dependencies = ['
  "env_logger",
  "format-bytes",
  "hg-core",
+ "lazy_static",
  "log",
  "micro-timer",
+ "regex",
  "users",
 ]
 

rust/rhg/Cargo.toml

@@ -12,8 +12,10 b' hg-core = { path = "../hg-core"}'
 chrono = "0.4.19"
 clap = "2.33.1"
 derive_more = "0.99"
+lazy_static = "1.4.0"
 log = "0.4.11"
 micro-timer = "0.3.1"
+regex = "1.3.9"
 env_logger = "0.7.1"
 format-bytes = "0.2.0"
 users = "0.11.0"

rust/rhg/src/main.rs

@@ -95,6 +95,25 b' fn main() {'
             exit(&ui, on_unsupported, Err(error.into()))
         });
 
+    if let Some(repo_path_bytes) = &early_args.repo {
+        lazy_static::lazy_static! {
+            static ref SCHEME_RE: regex::bytes::Regex =
+                // Same as `_matchscheme` in `mercurial/util.py`
+                regex::bytes::Regex::new("^[a-zA-Z0-9+.\\-]+:").unwrap();
+        }
+        if SCHEME_RE.is_match(&repo_path_bytes) {
+            exit(
+                &ui,
+                OnUnsupported::from_config(&non_repo_config),
+                Err(CommandError::UnsupportedFeature {
+                    message: format_bytes!(
+                        b"URL-like --repository {}",
+                        repo_path_bytes
+                    ),
+                }),
+            )
+        }
+    }
     let repo_path = early_args.repo.as_deref().map(get_path_from_bytes);
     let repo_result = match Repo::find(&non_repo_config, repo_path) {
         Ok(repo) => Ok(repo),