Strip pathspec and attribute-source settings from the walk's git (improvise-a0i3)

GIT_LITERAL/GLOB/NOGLOB/ICASE_PATHSPECS and GIT_ATTR_SOURCE are
process-wide, so --local-env-vars names none of them. Remove them in
git() beside the local-vars loop.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

tests/shipped_documents_load.rs

@@ -48,6 +48,15 @@ fn every_shipped_document_loads() {
     }
 }
 
+/// Settings that change how git reads a pathspec or finds attributes.
+const PATHSPEC_AND_ATTRIBUTE_SETTINGS: [&str; 5] = [
+    "GIT_LITERAL_PATHSPECS",
+    "GIT_GLOB_PATHSPECS",
+    "GIT_NOGLOB_PATHSPECS",
+    "GIT_ICASE_PATHSPECS",
+    "GIT_ATTR_SOURCE",
+];
+
 /// `git -C root`, with every repo-local variable a caller exported removed,
 /// since `GIT_DIR` and friends override `-C` (improvise-53zz).
 fn git(root: &Path) -> std::process::Command {
@@ -59,6 +68,10 @@ fn git(root: &Path) -> std::process::Command {
     for name in String::from_utf8(names.stdout).expect("UTF-8").lines() {
         git.env_remove(name);
     }
+    // Process-wide, so `--local-env-vars` lists none of them (improvise-a0i3).
+    for name in PATHSPEC_AND_ATTRIBUTE_SETTINGS {
+        git.env_remove(name);
+    }
     git.arg("-C").arg(root);
     git
 }