Error executing GIT command git commit

Frequently observing git issue when changing existing configuration. For example deactivate / disable a connection at distributed monitoring, I observe the following git error;

Error executing GIT command git commit --author "<first.last@domain.tld>" 
-m "Activating changes of Livestatus Proxy configuration, Modified site connection esxi, 
Modified site connection esxi":

On branch master
Your branch is up to date with 'upstream/master'.
Changes not staged for commit:

(use "git add <file>..." to update what will be committed)
(use "git restore <file>..." to discard changes in working directory)

modified: multisite.d/sites.mk
no changes added to commit (use "git add" and/or "git commit -a")

Command Line report, more or less the same.

OMD[mysite]:~/etc/check_mk$ git status
On branch master
Your branch is up to date with 'upstream/master'.

Changes not staged for commit:

  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)

        modified:   multisite.d/sites.mk
no changes added to commit (use "git add" and/or "git commit -a")

When I now revert the configuration, after activate in WATO, I do not observe any git issue (?) Changing anything again with the connection I got the git error again.

Any ideas, suggestions welcome.