git-config(1): clarify precedence of multiple values

In order to clarify which value is used when there are multiple values
defined for a key, re-order the list of file locations so that it runs
from least specific to most specific.  Then add a paragraph which simply
says that the last value will be used.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-config.txt

@@ -197,12 +197,8 @@ FILES
 If not set explicitly with '--file', there are four files where
 'git config' will search for configuration options:
 
-$GIT_DIR/config::
-	Repository specific configuration file.
-
-~/.gitconfig::
-	User-specific configuration file. Also called "global"
-	configuration file.
+$(prefix)/etc/gitconfig::
+	System-wide configuration file.
 
 $XDG_CONFIG_HOME/git/config::
 	Second user-specific configuration file. If $XDG_CONFIG_HOME is not set
@@ -212,8 +208,12 @@ $XDG_CONFIG_HOME/git/config::
 	you sometimes use older versions of Git, as support for this
 	file was added fairly recently.
 
-$(prefix)/etc/gitconfig::
-	System-wide configuration file.
+~/.gitconfig::
+	User-specific configuration file. Also called "global"
+	configuration file.
+
+$GIT_DIR/config::
+	Repository specific configuration file.
 
 If no further options are given, all reading options will read all of these
 files that are available. If the global or the system-wide configuration
@@ -221,6 +221,10 @@ file are not available they will be ignored. If the repository configuration
 file is not available or readable, 'git config' will exit with a non-zero
 error code. However, in neither case will an error message be issued.
 
+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.
+
 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*.