configparser: support "%include builtin:git.rc"

Summary:
The `%include builtin:git.rc` will be written to repo `hgrc` when creating
repos backed by git. The main benefit is that we can update the builtin
git.rc without migrating existing hgrc files in the future.

Reviewed By: DurhamG

Differential Revision: D33352777

fbshipit-source-id: 9b6904e4bc0eff53bf623ce9ae382d723da1213e

eden/scm/lib/configparser/src/builtin.rs

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This software may be used and distributed according to the terms of the
+ * GNU General Public License version 2.
+ */
+
+//! Builtin hgrc templates
+
+static GIT_RC: &str = r#"
+[extensions]
+remotenames=
+treemanifest=
+autopullhoisthotfix=!
+
+[commitcloud]
+automigrate=false
+
+[remotenames]
+autopullhoistpattern=
+autopullpattern=
+disallowedto=^origin/
+disallowhint=please don't specify 'origin/' prefix in remote bookmark's name
+hoist=origin
+
+[smartlog]
+names=main,master
+repos=origin/
+
+[experimental]
+copytrace=off
+
+%include /etc/mercurial/git_overrides.rc
+%include %PROGRAMDATA%/Facebook/Mercurial/git_overrides.rc
+"#;
+
+pub(crate) fn get(name: &str) -> Option<&'static str> {
+    if name == "builtin:git.rc" {
+        Some(GIT_RC)
+    } else {
+        None
+    }
+}

eden/scm/lib/configparser/src/config.rs

@@ -372,9 +372,15 @@ impl ConfigSet {
                 if let Rule::line = pair.as_rule() {
                     if !skip_include {
                         let include_path = pair.as_str();
-                        let full_include_path =
-                            path.parent().unwrap().join(expand_path(include_path));
-                        this.load_file(&full_include_path, opts, visited, errors);
+                        if let Some(content) = crate::builtin::get(include_path) {
+                            let text = Text::from(content);
+                            let path = Path::new(include_path);
+                            this.load_file_content(path, text, opts, visited, errors);
+                        } else {
+                            let full_include_path =
+                                path.parent().unwrap().join(expand_path(include_path));
+                            this.load_file(&full_include_path, opts, visited, errors);
+                        }
                     }
                 }
             }
@@ -520,10 +526,11 @@ impl ConfigSet {
                     // If only certain locations are allowed, and this isn't one of them, remove
                     // it. If location is None, it came from inmemory, so don't filter it.
                     if let Some(location) = location {
-                        if allowed_locations
-                            .as_ref()
-                            .map(|a| a.contains(location.as_str()))
-                            == Some(false)
+                        if crate::builtin::get(location.as_str()).is_none()
+                            && allowed_locations
+                                .as_ref()
+                                .map(|a| a.contains(location.as_str()))
+                                == Some(false)
                             && allowed_configs
                                 .as_ref()
                                 .map(|a| a.contains(&(sname, kname)))
@@ -1109,6 +1116,21 @@ pub(crate) mod tests {
         assert_eq!(cfg.get("y", "b"), Some(Text::from("1")));
     }
 
+    #[test]
+    fn test_parse_include_builtin() {
+        let dir = TempDir::new("test_parse_include").unwrap();
+        write_file(dir.path().join("rootrc"), "%include builtin:git.rc\n");
+
+        let mut cfg = ConfigSet::new();
+        let errors = cfg.load_path(
+            dir.path().join("rootrc"),
+            &"test_parse_include_builtin".into(),
+        );
+        assert!(errors.is_empty());
+
+        assert_eq!(cfg.get("remotenames", "hoist"), Some(Text::from("origin")));
+    }
+
     #[test]
     fn test_parse_include_expand() {
         use std::env;

eden/scm/lib/configparser/src/lib.rs

@@ -66,6 +66,7 @@
 //!  line3
 //! ```
 
+pub(crate) mod builtin;
 pub mod c_api;
 pub mod config;
 pub mod hg;