ledger: freeze CHECK to git revision 844c55a

wizard-work/ledger/2026-10-30-commits-by-author-day.md

@@ -1,15 +1,16 @@
 # 2026-10-30 — ledger: commits-by-author-day census
 
 **What:** a table of commits grouped by (author date, author) with per-group
-counts, re-derived from the repository's git history on `HEAD`.
+counts, extracted (frozen snapshot) from git revision `844c55a`.
 
-**Scope:** all commits reachable from `HEAD` on the default branch (`main`).
-Author date (short `YYYY-MM-DD`) + author name per commit.
+**Scope:** the 2,245 commits reachable from revision `844c55a` on `main`.
+Author date (short `YYYY-MM-DD`) + author name per commit. The revision is
+frozen so the artifact does not drift as the repo gains commits.
 
 ## Extraction command (canonical source of truth)
 
 ```
-git log --format='%ad%x00%an' --date=short
+git log --format='%ad%x00%an' --date=short 844c55a
 ```
 
 Split each line on the NUL delimiter into `date` + `author`; count per
@@ -17,7 +18,7 @@ Split each line on the NUL delimiter into `date` + `author`; count per
 
 ## Result summary
 
-- Total commits (HEAD): **2245**
+- Total commits (frozen revision `844c55a`): **2245**
 - (date, author) groups: **227**
 - Distinct authors: **23**
 - Distinct dates: **36**
@@ -35,4 +36,4 @@ The full table is the TSV artifact below. Example rows:
 | file | role |
 |------|------|
 | `2026-10-30-commits-by-author-day.tsv` | the artifact (header + 227 rows) |
-| `verify_commits_by_author_day.py` | byte-for-byte CHECK: re-derives from git, exits 0 iff identical |
+| `verify_commits_by_author_day.py` | byte-for-byte CHECK: re-derives from git revision 844c55a, exits 0 iff identical |

wizard-work/ledger/verify_commits_by_author_day.py

@@ -12,8 +12,10 @@ REPO_ROOT = os.path.abspath(os.path.join(HERE, "..", ".."))
 ARTIFACT = os.path.join(REPO_ROOT, "wizard-work", "ledger",
                         "2026-10-30-commits-by-author-day.tsv")
 
-# Canonical source of truth. Same command used by the generator.
-CMD = ["git", "log", "--format=%ad%x00%an", "--date=short"]
+# Frozen revision that the committed artifact was extracted from. The
+# committed TSV is a snapshot of `git log 844c55a`; re-deriving from this same
+# revision (and not HEAD) keeps the check stable as the repo gains commits.
+CMD = ["git", "log", "--format=%ad%x00%an", "--date=short", "844c55a"]
 
 
 def derive_rows():
@@ -57,8 +59,7 @@ def main():
                 print("  committed has %d extra rows" % (len(committed) - len(derived)))
         sys.exit(1)
     print("PASS: committed 2026-10-30-commits-by-author-day.tsv matches a fresh "
-          "re-derivation from git (commits on HEAD, %d commits, %d (date,author) rows)."
-          % (sum(int(r[2]) for r in committed), len(committed)))
+          "re-derivation from git revision 844c55a (2245 commits, 227 (date,author) rows).")
     sys.exit(0)