feat: Parse Go-style diffs

src/step/check_parsing.rs

@@ -11,6 +11,7 @@ use std::collections::HashSet;
 use std::path::PathBuf;
 use xx::file::display_path;
 
+use super::strip_orig_suffix;
 use super::types::Step;
 
 /// Attempt to canonicalize a path, falling back to the original if it fails.
@@ -89,6 +90,8 @@ impl Step {
         original_files: &[PathBuf],
         stdout: &str,
     ) -> (Vec<PathBuf>, Vec<PathBuf>) {
+        let stdout = strip_orig_suffix(stdout);
+
         // Parse unified diff format to extract file names from --- and +++ lines
         let mut listed: HashSet<PathBuf> = HashSet::new();
 

src/step/diff.rs

@@ -7,6 +7,7 @@
 use crate::Result;
 use std::io::Write;
 
+use super::strip_orig_suffix;
 use super::types::Step;
 
 impl Step {
@@ -19,6 +20,9 @@ impl Step {
     /// Automatically detects whether the diff uses `a/` and `b/` prefixes (git-style)
     /// and sets the appropriate strip level (`-p1` or `-p0`).
     ///
+    /// Also handles Go-style diffs where the `---` line has a `.orig` suffix
+    /// (e.g., `--- file.go.orig` instead of `--- file.go`).
+    ///
     /// # Arguments
     ///
     /// * `stdout` - The unified diff output from the check_diff command
@@ -33,7 +37,7 @@ impl Step {
             debug!("{}: no diff content to apply", self.name);
             return Ok(false);
         }
-        let diff_content = stdout;
+        let diff_content = strip_orig_suffix(stdout);
 
         // Detect if this diff uses a/ and b/ prefixes (git-style)
         // Use -p1 to strip prefixes if present, -p0 otherwise

src/step/mod.rs

@@ -52,3 +52,22 @@ pub use types::{OutputSummary, Pattern, RunType, Script, Step};
 // Re-export for potential external use (currently only used internally)
 #[allow(unused_imports)]
 pub use filtering::{is_binary_file, is_symlink_file};
+
+/// Strip ".orig" from "---" lines when the next "+++" line doesn't have it.
+/// Go tools like gofmt add ".orig" only to the "---" line.
+pub(crate) fn strip_orig_suffix(diff: &str) -> String {
+    let mut result: Vec<String> = Vec::new();
+    let mut lines = diff.lines().peekable();
+    while let Some(line) = lines.next() {
+        if line.starts_with("--- ") && line.contains(".orig") {
+            if let Some(next) = lines.peek() {
+                if next.starts_with("+++ ") && !next.contains(".orig") {
+                    result.push(line.replace(".orig", ""));
+                    continue;
+                }
+            }
+        }
+        result.push(line.to_string());
+    }
+    result.join("\n") + "\n"
+}

test/apply_check_diff.bats

@@ -60,15 +60,12 @@ EOF
     # Create a file without trailing newline
     printf "hello" > test.txt
 
-    git add .
-    git commit -m "initial"
-
     # Run fix
     run hk fix test.txt
     assert_success
 
     # The file should have a newline added (from the diff), NOT "FIXED:" prefix
-    # If git apply worked, content is "hello\n"
+    # If the apply worked, content is "hello\n"
     # If fixer ran, content would be "FIXED:hello"
     run cat test.txt
     assert_output "hello"  # With newline from diff
@@ -78,7 +75,7 @@ EOF
     assert_failure
 }
 
-@test "check_diff falls back to fixer when git apply fails" {
+@test "check_diff falls back to fixer when apply fails" {
     # Create a "formatter" that outputs invalid diff
     cat <<'SCRIPT' > formatter.sh
 #!/bin/bash
@@ -114,9 +111,6 @@ EOF
 
     echo "hello" > test.txt
 
-    git add .
-    git commit -m "initial"
-
     # Run fix - should fall back to fixer since diff is invalid
     run hk fix test.txt
     assert_success
@@ -171,8 +165,6 @@ hooks {
 EOF
 
     echo "original" > test.txt
-    git add .
-    git commit -m "initial"
 
     run hk fix test.txt
     assert_success
@@ -222,8 +214,6 @@ hooks {
 EOF
 
     echo "original" > test.txt
-    git add .
-    git commit -m "initial"
 
     # Run CHECK (not fix) - should fail but NOT modify the file
     run hk check test.txt
@@ -281,8 +271,6 @@ hooks {
 EOF
 
     echo "original" > test.txt
-    git add .
-    git commit -m "initial"
 
     run hk fix test.txt
     assert_success
@@ -293,7 +281,7 @@ EOF
 }
 
 @test "check_diff handles diffs without a/b prefixes" {
-    # Some tools output diffs without the git-style a/ and b/ prefixes
+    # Some tools output diffs without the a/ and b/ prefixes
     # e.g., "--- src/file.py" instead of "--- a/src/file.py"
     cat <<'SCRIPT' > formatter.sh
 #!/bin/bash
@@ -333,13 +321,106 @@ hooks {
 EOF
 
     echo "original" > test.txt
-    git add .
-    git commit -m "initial"
-
     run hk fix test.txt
     assert_success
 
     # Verify the diff was applied (uses -p0 since no a/b prefixes)
     run cat test.txt
     assert_output "no_prefix_diff"
 }
+
+@test "check_diff handles diffs with .orig suffix on --- line" {
+    # Go tools like gofmt output diffs with .orig suffix on the --- line
+    # e.g., "--- file.go.orig" instead of "--- file.go"
+    cat <<'SCRIPT' > formatter.sh
+#!/bin/bash
+file="$1"
+if [ -f "$file" ]; then
+    # Output diff with .orig suffix (like gofmt -d)
+    echo "--- $file.orig"
+    echo "+++ $file"
+    echo "@@ -1 +1 @@"
+    echo "-$(cat "$file")"
+    echo "+gofmt_fixed"
+fi
+exit 1
+SCRIPT
+    chmod +x formatter.sh
+
+    cat <<'SCRIPT' > fixer.sh
+#!/bin/bash
+echo "FIXER_RAN" > "$1"
+SCRIPT
+    chmod +x fixer.sh
+
+    cat <<EOF > hk.pkl
+amends "$PKL_PATH/Config.pkl"
+hooks {
+    ["fix"] {
+        fix = true
+        steps {
+            ["fmt"] {
+                glob = List("*.go")
+                check_diff = "./formatter.sh {{files}}"
+                fix = "./fixer.sh {{files}}"
+            }
+        }
+    }
+}
+EOF
+
+    echo "original" > test.go
+
+    run hk fix test.go
+    assert_success
+
+    # Verify the diff was applied (should strip .orig suffix)
+    run cat test.go
+    assert_output "gofmt_fixed"
+}
+
+@test "check_diff works if the file has .orig suffix" {
+    cat <<'SCRIPT' > formatter.sh
+#!/bin/bash
+file="$1"
+if [ -f "$file" ]; then
+    echo "--- $file"
+    echo "+++ $file"
+    echo "@@ -1 +1 @@"
+    echo "-$(cat "$file")"
+    echo "+diffed"
+fi
+exit 1
+SCRIPT
+    chmod +x formatter.sh
+
+    cat <<'SCRIPT' > fixer.sh
+#!/bin/bash
+echo "FIXER_RAN" > "$1"
+SCRIPT
+    chmod +x fixer.sh
+
+    cat <<EOF > hk.pkl
+amends "$PKL_PATH/Config.pkl"
+hooks {
+    ["fix"] {
+        fix = true
+        steps {
+            ["fmt"] {
+                glob = List("*.orig")
+                check_diff = "./formatter.sh {{files}}"
+                fix = "./fixer.sh {{files}}"
+            }
+        }
+    }
+}
+EOF
+
+    echo "original" > test.orig
+
+    run hk fix test.orig
+    assert_success
+
+    run cat test.orig
+    assert_output "diffed"
+}