Restructure db schema

The "commit_links" table is now called "commit_edges".

There is now a "metrics" table that run measurements have a foreign key
to. This provides canonical metric metadata and will speed up the
initial graph page (before any real data arrives). For now, it will be
overwritten with each new run, but more nuanced config options may be
added later.

src/server/web/pages/commit.rs

@@ -50,7 +50,7 @@ pub async fn get_commit_by_hash(
     let parents = sqlx::query!(
         "\
         SELECT hash, message, reachable FROM commits \
-        JOIN commit_links ON hash = parent \
+        JOIN commit_edges ON hash = parent \
         WHERE child = ? \
         ORDER BY reachable DESC, unixepoch(committer_date) ASC \
         ",
@@ -64,7 +64,7 @@ pub async fn get_commit_by_hash(
     let children = sqlx::query!(
         "\
         SELECT hash, message, reachable FROM commits \
-        JOIN commit_links ON hash = child \
+        JOIN commit_edges ON hash = child \
         WHERE parent = ? \
         ORDER BY reachable DESC, unixepoch(committer_date) ASC \
         ",