When I was working on a repo, something strange occurred.

# Local repo
$ git log --oneline -3
4030437 (HEAD -> optimize_dumpUi) Optimize assert button exist method
6a23ff5 (upstream/master, master) Merge branch 'issue_update_unit' of JaedenKil/Perf-MLBench-DEBUSQA into master
b21a7af (origin/issue_update_unit, issue_update_unit) Update test result unit

# Remote repo
$ git log origin/optimize_dumpUi --oneline -3
f9b9099 (origin/optimize_dumpUi) Optimize assert button exist method
6a23ff5 (upstream/master, master) Merge branch 'issue_update_unit' of JaedenKil/Perf-MLBench-DEBUSQA into master
b21a7af (origin/issue_update_unit, issue_update_unit) Update test result unit

After a check, found the newest commit of both repositories are exactly the same except for the commit id.
So:

$ git reflog -6
4030437 (HEAD -> optimize_dumpUi) HEAD@{0}: commit (amend): Optimize assert button exist method
f9b9099 (origin/optimize_dumpUi) HEAD@{1}: commit: Optimize assert button exist method
6a23ff5 (upstream/master, master) HEAD@{2}: checkout: moving from master to optimize_dumpUi
6a23ff5 (upstream/master, master) HEAD@{3}: merge upstream/master: Fast-forward
179091b (origin/master) HEAD@{4}: checkout: moving from issue_update_unit to master
b21a7af (origin/issue_update_unit, issue_update_unit) HEAD@{5}: commit: Update test result unit

Finally, commit (amend) shows I made a commit, then used git commit --amend, thus leading to different commit id.

git diff f9b90 40304
...
-            Log.i(TAG, prefix + "Target UiObject '" + objName + " exists.");
+            Log.i(TAG, prefix + "Target UiObject '" + objName + "' exists.");

So the problem was caused by adding a colon...
In the end, git push -f is needed. Luckily this is not on the master branch.