Fix pony-lint ignore matching on Windows

The ignore matcher hardcoded `/` as the path separator in three places,
causing all ignore rules to silently fail on Windows where paths use `\`.

Closes #5053

Author: SeanTAllen

.release-notes/fix-pony-lint-windows-ignore.md

@@ -0,0 +1,3 @@
+## Fix pony-lint ignore matching on Windows
+
+pony-lint's `.gitignore` and `.ignore` pattern matching failed on Windows because path separator handling was hardcoded to `/`. On Windows, where paths use `\`, ignore rules were silently ineffective — files that should have been skipped were linted, and anchored patterns like `src/build/` never matched.

tools/pony-lint/ignore_matcher.pony

@@ -126,10 +126,18 @@ class ref IgnoreMatcher
 
         let matched =
           if pat.anchored then
-            // Match against path relative to the rule's base directory
+            // Match against path relative to the rule's base directory,
+            // normalized to forward slashes for GlobMatch
             let rel =
               try
-                Path.rel(base_dir, abs_path)?
+                let r = Path.rel(base_dir, abs_path)?
+                ifdef windows then
+                  let s = r.clone()
+                  s.replace("\\", "/")
+                  consume s
+                else
+                  r
+                end
               else
                 abs_path
               end
@@ -154,9 +162,9 @@ class ref IgnoreMatcher
     """
     if abs_path.at(base_dir) then
       let blen = base_dir.size()
-      // Exact match or path continues with /
+      // Exact match or path continues with a separator
       (abs_path.size() == blen)
-        or (try abs_path(blen)? == '/' else false end)
+        or (try Path.is_sep(abs_path(blen)?) else false end)
     else
       false
     end

tools/pony-lint/linter.pony

@@ -457,7 +457,7 @@ class val Linter
       else
         return
       end
-    let parts = rel.split_by("/")
+    let parts = rel.split_by(Path.sep())
     var current: String val = root
     for part in (consume parts).values() do
       current = Path.join(current, part)