Centralize DIST_DIR-derived paths via working_dir/exif_cache_dir helpers

The EXIF cache dir ($(dirname "$DIST_DIR")/cache/exif) was recomputed inline,
byte for byte, in both cached_photo_identify_output (read/write) and
clear_exif_cache (--force/--clean removal). The plain parent of DIST_DIR
(dirname "$DIST_DIR") was likewise recomputed in metadata-cache and in
action.source.sh's staging-artifact cleanup.

Extract two helpers computed once from DIST_DIR:
  - working_dir() in config.source.sh (next to existing_parent_dir, the other
    DIST_DIR-parent resolver): plain `dirname "$DIST_DIR"`.
  - exif_cache_dir() in metadata-cache.source.sh (owns the EXIF cache):
    `working_dir()/cache/exif`.

Route cached_photo_identify_output, clear_exif_cache, and
clean_generation_staging_artifacts through them so the cache reader and the
cleaner can never drift to different directories. Paths are byte-identical to
the prior inline code (dirname semantics, cache/exif suffix, trailing-slash and
relative/absolute handling all preserved). Stale "recompute the cache dir"
comments removed; helpers document the path once. Add a unit test asserting the
helpers agree and resolve beside dist for several DIST_DIR shapes.

Broader DIST_DIR parameterization of leaf pipeline helpers was intentionally
left out of scope (only the duplicated path computation is centralized here).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/cli.sh b/tests/cli.sh
index 2280a7e..c8cbd36 100755
--- a/tests/cli.sh
+++ b/tests/cli.sh
@@ -6396,6 +6396,31 @@ test::source_shuriken_lib() {
     source <(sed '$d' "$TEST_SHURIKEN")
 }
 
+# pr0: the EXIF cache dir is computed once via exif_cache_dir() (= working_dir()/
+# cache/exif, where working_dir() is dirname "$DIST_DIR"). Both the cache
+# reader/writer and the --force/--clean cleaner route through this single helper,
+# so they can never point at different directories. Assert the helpers agree and
+# resolve to the documented "sibling of dist" path for a few DIST_DIR shapes.
+test_exif_cache_dir_resolves_beside_dist() {
+    test::setup
+    test::source_shuriken_lib
+
+    DIST_DIR='/home/u/site/dist'
+    test "$(working_dir)" = '/home/u/site'
+    test "$(exif_cache_dir)" = '/home/u/site/cache/exif'
+
+    # Relative DIST_DIR keeps dirname semantics (parent is ".").
+    DIST_DIR='dist'
+    test "$(working_dir)" = '.'
+    test "$(exif_cache_dir)" = './cache/exif'
+
+    # A trailing slash is collapsed exactly as dirname collapses it.
+    DIST_DIR='a/b/dist/'
+    test "$(exif_cache_dir)" = 'a/b/cache/exif'
+
+    test::teardown
+}
+
 test_stats_aggregates_synthetic_exif_fixtures() {
     local fixture
 
@@ -7188,6 +7213,9 @@ main() {
         '--generate reuses cached EXIF details unless forced' \
         test_generate_reuses_cached_exif_details_unless_forced
     test::run_case \
+        'EXIF cache dir resolves beside dist' \
+        test_exif_cache_dir_resolves_beside_dist
+    test::run_case \
         'stats aggregate synthetic EXIF fixtures' \
         test_stats_aggregates_synthetic_exif_fixtures
     test::run_case \