adds conflicts section

basics.html

@@ -754,13 +754,32 @@
           </section>
 
           <section id="collab-conflicts" data-markdown>
-            ## conflicts
+            ## resolving conflicts
+            ### maintainer
+
+            ```bash
+            git remote add alice https://...
+            git fetch alice
+            git checkout master
+            git merge alice/topic/feature
+            # fix conflicts
+            git push
+            ```
+
+            ### contributor
+
+            ```bash
+            git fetch upstream
+            git checkout topic/feature
+            git merge origin/master
+            # fix conflicts
+            git push
+            ```
 
             notes:
             - hopefully conflicting changes
             - MR status should show that (can not be merged without conflicts)
-            - TODO explain merge or rebase
-            - TODO show both variants from maintainer and contributor
+            - maintainer decides if trivial or delegate to contributor
           </section>
         </section>