Incremental voomdb updates were done incorrectly, creating corrupt data

Our use of git fast-export caused the oldest commit(s) imported to claim a
change for every file in the repo. We now use import-marks to stop that
behavior.

Note the db header bump is not because the structure of the db changed, but
rather to trigger the removal of old and possibly corrupt dbs.

src/leiningen/voom.clj

@@ -851,17 +851,27 @@
 
 (defn exported-commits
   [gitdir tip-shas seen-shas]
-  (let [marks-file (File/createTempFile "marks" ".txt")]
+  (let [long-sha (fn [sha] (first (:lines (git {:gitdir gitdir} "rev-parse" (str sha)))))
+        out-marks-file (File/createTempFile "out-marks" ".txt")
+        in-marks-file (File/createTempFile "in-marks" ".txt")]
     (try
-      (let [{:keys [out]} (apply sh "git" "fast-export" "--no-data"
-                                 (str "--export-marks=" marks-file)
-                                 (concat (map str tip-shas)
-                                         (map #(str "^" %) seen-shas)
-                                         [:dir gitdir, :out-enc :bytes]))
+      (spit in-marks-file
+            (apply str (map-indexed (fn [i sha]
+                                      (str ":" (inc i) " " (long-sha sha) "\n"))
+                                    seen-shas)))
+      (let [{:keys [out] :as rtn} (apply sh "git" "fast-export" "--no-data"
+                                         (str "--export-marks=" out-marks-file)
+                                         (concat
+                                          (when (seq seen-shas)
+                                            [(str "--import-marks=" in-marks-file)])
+                                          (map str tip-shas)
+                                          (map #(str "^" %) seen-shas)
+                                          [:dir gitdir, :out-enc :bytes]))
+            _ (assert (zero? (:exit rtn)) (pr-str (:err rtn)))
             marks (into {}
                         (map #(let [[mark sha] (s/split % #" ")]
                                 [mark (sha/mk sha)])
-                             (re-seq #"(?m)^.*$" (slurp marks-file))))
+                             (re-seq #"(?m)^.*$" (slurp out-marks-file))))
             merge-commit-fn (fn [cmd commit]
                               (if (= cmd "merge")
                                 (-> commit
@@ -906,7 +916,8 @@
                                commit)))))
               commits))))
       (finally
-       (.delete marks-file)))))
+       (.delete in-marks-file)
+       (.delete out-marks-file)))))
 
 (defn proj-fact-tail
   [gitdir blob-sha]
@@ -987,7 +998,7 @@
           (build-shabam (vals new-branches))
           (vary-meta assoc ::dirty true))))))
 
-(def voomdb-header "voom-db-7")
+(def voomdb-header "voom-db-8")
 
 (defn ^File git-db-file
   [gitdir]