Fix gitgraph branch continues after merge (go-gitea#12044) (go-gitea#12105)

Backport go-gitea#12044

* Fix gitgraph branch continues after merge

After fixing the initial problem in go-gitea#11981 another
problem has come to light...

Fix go-gitea#11981 (part 2)

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Update web_src/js/vendor/gitgraph.js

* Apply suggestions from code review

Co-authored-by: silverwind <me@silverwind.io>

Author: zeripath

web_src/js/vendor/gitgraph.js

@@ -372,6 +372,10 @@ export default function gitGraph(canvas, rawGraphList, config) {
           inlineIntersect = false;
         }
 
+        if (colomn === '|' && currentRow[colomnIndex - 1] && currentRow[colomnIndex - 1] === '\\') {
+          flows.splice(colomnIndex, 0, genNewFlow());
+        }
+
         color = flows[colomnIndex].color;
 
         switch (colomn) {
@@ -387,6 +391,9 @@ export default function gitGraph(canvas, rawGraphList, config) {
             break;
 
           case '|':
+            if (prevColomn && prevColomn === '\\') {
+              x += config.unitSize;
+            }
             drawLineUp(x, y, color);
             break;