cli: expand ~ in core.excludesFile, don't crash when missing

I thought that `std::fs::canonicalize()` expanded "~", but it doesn't
seem to do that, which caused #131. Git seems to do the expansion
itself, so we probably also should. More importantly
`std::fs::canonicalize()` crashes when the file doesn't exist. The
manual expansion we do now does not.

Closes #131.

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed bugs
+
+ - (#131) Fixed crash when `core.excludesFile` pointed to non-existent file, and
+   made leading `~/` in that config expand to `$HOME/`
+
 ## [0.3.0] - 2022-03-12
 
 Last release before this changelog started.

src/commands.rs

@@ -396,8 +396,7 @@ impl WorkspaceCommandHelper {
             .git_config()
             .and_then(|git_config| git_config.get_string("core.excludesFile"))
         {
-            let excludes_file_path =
-                std::fs::canonicalize(PathBuf::from(excludes_file_str)).unwrap();
+            let excludes_file_path = expand_git_path(excludes_file_str);
             git_ignores = git_ignores.chain_with_file("", excludes_file_path);
         }
         if let Some(git_repo) = self.repo.store().git_repo() {
@@ -708,6 +707,16 @@ impl WorkspaceCommandHelper {
     }
 }
 
+/// Expands "~/" to "$HOME/" as Git seems to do for e.g. core.excludesFile.
+fn expand_git_path(path_str: String) -> PathBuf {
+    if let Some(remainder) = path_str.strip_prefix("~/") {
+        if let Ok(home_dir_str) = std::env::var("HOME") {
+            return PathBuf::from(home_dir_str).join(remainder);
+        }
+    }
+    PathBuf::from(path_str)
+}
+
 fn rev_arg<'help>() -> Arg<'help> {
     Arg::new("revision")
         .long("revision")

src/testutils.rs

@@ -31,6 +31,7 @@ impl Default for TestEnvironment {
         let tmp_dir = TempDir::new().unwrap();
         let env_root = tmp_dir.path().canonicalize().unwrap();
         let home_dir = env_root.join("home");
+        std::fs::create_dir(&home_dir).unwrap();
         Self {
             _temp_dir: tmp_dir,
             env_root,

tests/test_gitignores.rs

@@ -31,24 +31,15 @@ fn test_gitignores() {
         .append(true)
         .open(workspace_root.join(".git").join("config"))
         .unwrap();
-    let excludes_file_path = test_env
-        .env_root()
-        .join("my-ignores")
-        .to_str()
-        .unwrap()
-        .to_string();
-    file.write_all(
-        format!(
-            "[core]\nexcludesFile=\"{}\"",
-            excludes_file_path
-                .replace('\\', "\\\\")
-                .replace('\"', "\\\"")
-        )
-        .as_bytes(),
+    // Put the file in "~/my-ignores" so we also test that "~" expands to "$HOME"
+    file.write_all(b"[core]\nexcludesFile=~/my-ignores\n")
+        .unwrap();
+    drop(file);
+    std::fs::write(
+        test_env.home_dir().join("my-ignores"),
+        "file1\nfile2\nfile3",
     )
     .unwrap();
-    drop(file);
-    std::fs::write(excludes_file_path, "file1\nfile2\nfile3").unwrap();
 
     // Say in .git/info/exclude that we actually do want file2 and file3
     let mut file = std::fs::OpenOptions::new()