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

context/test-evidence/tui.md

@@ -610,6 +610,47 @@ the `-c` arguments in `run_git` beat relying on the absence of a config file.
 
 Rival: drop `--template=`. Red, as above.
 
+### the_walk_ignores_the_users_pathspec_and_attribute_settings
+
+improvise-a0i3. `git(root)` strips what `git rev-parse --local-env-vars` names,
+and that list holds only the variables that point at a repository (`GIT_DIR`,
+`GIT_INDEX_FILE` and so on). Pathspec magic and the attribute source are
+process-wide settings, so the list names none of them. They still change what
+`git ls-files -- '*.improv' '*.improv.gz'` answers:
+
+- `GIT_LITERAL_PATHSPECS=1` reads `*.improv` as a file literally named
+  `*.improv`, so the walk finds nothing.
+- `GIT_GLOB_PATHSPECS=1` stops `*` at `/`, so only a document at the root
+  matches. `GIT_NOGLOB_PATHSPECS=1` reads `*` literally, like the literal
+  setting. Every document these tests walk sits below the root, so both
+  settings made both tests fail.
+- `GIT_ATTR_SOURCE=HEAD` makes git read attributes from `HEAD`. The scratch
+  repository in the gzip shape test has no commit, so `git add` fails with
+  `bad --attr-source`.
+
+The test reruns `a_gzipped_document_is_walked` and `every_shipped_document_loads`
+in a child under each of five settings, which is ten runs, and collects every
+failure before it asserts. Red at #260's head `322de370`: 7 of 10 runs failed.
+`LITERAL`, `GLOB` and `NOGLOB` each broke both tests. `ATTR_SOURCE` broke only
+the gzip shape test, because the real checkout has a `HEAD`. The ticket reported
+`ATTR_SOURCE` breaking both tests. Here it broke one, so the difference is in
+the checkout the ticket measured, not in the fix.
+
+The fix is to remove the five variables in `git()`, next to the
+`--local-env-vars` loop. A `--literal-pathspecs`-style command-line flag would
+have to be chosen per variable, and `GIT_ATTR_SOURCE` has no negating flag.
+
+Rivals, each dropping one name from `PATHSPEC_AND_ATTRIBUTE_SETTINGS`:
+
+- Without `GIT_LITERAL_PATHSPECS`, `GIT_GLOB_PATHSPECS` or
+  `GIT_NOGLOB_PATHSPECS`: red, both tests under that setting.
+- Without `GIT_ATTR_SOURCE`: red, the gzip shape test.
+- Without `GIT_ICASE_PATHSPECS`: **green.** A case-insensitive match of
+  `*.improv` still finds every document, so this row of the test cannot fail.
+  The name stays in the list because it is the fourth of git's pathspec
+  variables, and a future spelling of the walk that depends on case would be
+  exposed to it. The test covers it, but that coverage is vacuous today.
+
 ---
 
 ## `tests/web_demo_model.rs`

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
 }