mn0 share camera Make+Model dedup helper

The rule that joins a camera's EXIF Make + Model into one label while
avoiding a duplicated manufacturer prefix (e.g. "Canon Canon EOS 5D" ->
"Canon EOS 5D") was implemented independently in the album tooltip builder
and the stats leaderboard tally. Extract it into a single shared helper
camera_label_from_make_model in the new src/lib/metadata-label.source.sh,
sourced before both callers.

Both prior implementations were behavior-identical (empty model -> make,
empty make -> model, exact/prefix dedup, case-sensitive), so this is a pure
DRY refactor with no observable output change. Added a focused unit test
covering dedup, plain concatenation and the empty-field edge cases.

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

1 files changed, 31 insertions, 0 deletions

diff --git a/src/lib/metadata-label.source.sh b/src/lib/metadata-label.source.sh
new file mode 100644
index 0000000..4d36b3c
--- /dev/null
+++ b/src/lib/metadata-label.source.sh
@@ -0,0 +1,31 @@
+# Shared EXIF metadata label helpers. Extracted (task mn0) so the rule for
+# turning a camera's Make + Model into one human-readable label lives in a
+# single place instead of being duplicated in album-metadata.source.sh's
+# tooltip builder and stats-aggregate.source.sh's leaderboard tally. This file
+# is sourced before both callers (see LIB_SOURCES in the Justfile). All library
+# modules are sourced before any code runs, so definition order only documents
+# the dependency, it does not affect availability.
+
+# Join a camera's EXIF Make + Model into one label, avoiding a duplicated
+# manufacturer prefix. Many cameras already repeat the make inside the model
+# (e.g. Make="Canon", Model="Canon EOS 5D"), so when the model equals the make
+# or starts with "<make> " we keep the model alone ("Canon EOS 5D" rather than
+# "Canon Canon EOS 5D"). Either field may be empty: an empty model yields the
+# make, an empty make yields the model, and both empty yields an empty string.
+camera_label_from_make_model() {
+    local -r make="$1"; shift
+    local -r model="$1"; shift
+
+    if [ -z "$model" ]; then
+        printf '%s' "$make"
+        return
+    fi
+    if [ -z "$make" ]; then
+        printf '%s' "$model"
+        return
+    fi
+    case "$model" in
+        "$make"|"$make "*) printf '%s' "$model" ;;
+        *) printf '%s %s' "$make" "$model" ;;
+    esac
+}