The filetype of 'gitcommit' file will be changed to 'conf' after :w

[linjiX]

Does this bug happen when you install plugin without vim-polyglot?
No

Describe the bug:
This issue happens after 1150adc

The gitcommit file will be correctly detected as gitcommit, but the filetype will be changed to conf after writing file

To Reproduce:

1. Execute git commit to open a gitcommit file in Vim

git commit

2. Check the filetype

:set filetype?

The result should be filetype=gitcommit, which is correct.

3. Write file

:w

4. Check the filetype again

:set filetype?

The result changes to filetype=conf, which is incorrect.