Catch whitespace code style violations locally (#774)

Those settings enforce convergence on common coding style with respect to whitespace.

Do not use tabs to indent with shell scripts because those tabs most often
serve the function of triggering command completion. Which could end a
command before it is pasted completely.
  Traditionally indentation is two spaces here, not four.

Other rules will catch stray whitespace at the end of lines or files, which,
once committed, would annoy the next developer because his editor would strip
them from lines he did not intended to modify in the first place.

.gitattributes

-*.bash    text eol=lf whitespace=blank-at-eol,space-before-tab,tab-in-indent,trailing-space,tabwidth=4
-*.sh      text eol=lf whitespace=blank-at-eol,space-before-tab,tab-in-indent,trailing-space,tabwidth=4
+# shell scripts should not use tabs to indent!
+*.bash    text eol=lf core.whitespace whitespace=tab-in-indent,trailing-space,tabwidth=2
+*.sh      text eol=lf core.whitespace whitespace=tab-in-indent,trailing-space,tabwidth=2
 
-# files for systemd
-*.path    text eol=lf whitespace=blank-at-eol,space-before-tab,tab-in-indent,trailing-space,tabwidth=4
-*.service text eol=lf whitespace=blank-at-eol,space-before-tab,tab-in-indent,trailing-space,tabwidth=4
-*.timer   text eol=lf whitespace=blank-at-eol,space-before-tab,tab-in-indent,trailing-space,tabwidth=4
+# files for systemd (shell-similar)
+*.path    text eol=lf core.whitespace whitespace=tab-in-indent,trailing-space,tabwidth=2
+*.service text eol=lf core.whitespace whitespace=tab-in-indent,trailing-space,tabwidth=2
+*.timer   text eol=lf core.whitespace whitespace=tab-in-indent,trailing-space,tabwidth=2
+
+# go fmt will enforce this, but in case a user has not called "go fmt" allow GIT to catch this:
+*.go      text eol=lf core.whitespace whitespace=indent-with-non-tab,trailing-space,tabwidth=4
+
+*.yml     text eol=lf core.whitespace whitespace=tab-in-indent,trailing-space,tabwidth=2
+.git*     text eol=auto core.whitespace whitespace=trailing-space