Merge branch 'dg/document-git-c-in-git-config-doc'

The "git -c var[=val] cmd" facility to append a configuration
variable definition at the end of the search order was described in
git(1) manual page, but not in git-config(1), which was more likely
place for people to look for when they ask "can I make a one-shot
override, and if so how?"

* dg/document-git-c-in-git-config-doc:
  doc: mention `git -c` in git-config(1)

Documentation/git-config.txt

@@ -263,6 +263,9 @@ The files are read in the order given above, with last value found taking
 precedence over values read earlier.  When multiple values are taken then all
 values of a key from all files will be used.
 
+You may override individual configuration parameters when running any git
+command by using the `-c` option. See linkgit:git[1] for details.
+
 All writing options will per default write to the repository specific
 configuration file. Note that this also affects options like `--replace-all`
 and `--unset`. *'git config' will only ever change one file at a time*.