feat(data): added sha256 for data provenance

analysis/gen_values.py

@@ -6,6 +6,7 @@ one \\pgfkeys block; sources are recorded in the header for provenance.
 """
 import argparse
 import datetime as dt
+import hashlib
 import importlib.util
 from pathlib import Path
 from types import ModuleType
@@ -29,6 +30,14 @@ def file_mtime_iso(p: Path) -> str:
     return dt.datetime.fromtimestamp(p.stat().st_mtime).isoformat(timespec="seconds")
 
 
+def file_sha256(p: Path) -> str:
+    h = hashlib.sha256()
+    with p.open("rb") as f:
+        for chunk in iter(lambda: f.read(1 << 16), b""):
+            h.update(chunk)
+    return h.hexdigest()
+
+
 # Map key-name suffix to siunitx unit. 
 UNIT_SUFFIXES = {
     "-us":   r"\micro\second",
@@ -87,7 +96,7 @@ def main() -> None:
         all_keys.update(keys)
         provenance.append(f"%   {name}: {len(keys)} keys")
         for src in sources:
-            provenance.append(f"%     {src} (mtime {file_mtime_iso(src)})")
+            provenance.append(f"%     {src} (mtime {file_mtime_iso(src)}, sha256 {file_sha256(src)})")
         print(f"  {name}: {len(keys)} keys from {len(sources)} sources")
 
     args.out.parent.mkdir(parents=True, exist_ok=True)