Windows: Fix path separator of GIT_ALTERNATE_OBJECT_DIRECTORIES.

For consistency and technical reasons on Windows (':' is usually part of directory
names), we must use ';' as path separator.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>

Documentation/git.txt

@@ -375,9 +375,9 @@ git so take care if using Cogito etc.
 'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 	Due to the immutable nature of git objects, old objects can be
 	archived into shared, read-only directories. This variable
-	specifies a ":" separated list of git object directories which
-	can be used to search for git objects. New objects will not be
-	written to these directories.
+	specifies a ":" separated (on Windows ";" separated) list
+	of git object directories which can be used to search for git
+	objects. New objects will not be written to these directories.
 
 'GIT_DIR'::
 	If the 'GIT_DIR' environment variable is set then it

sha1_file.c

@@ -395,7 +395,11 @@ void prepare_alt_odb(void)
 	if (!alt) alt = "";
 
 	alt_odb_tail = &alt_odb_list;
+#ifdef __MINGW32__
+	link_alt_odb_entries(alt, alt + strlen(alt), ';', NULL, 0);
+#else
 	link_alt_odb_entries(alt, alt + strlen(alt), ':', NULL, 0);
+#endif
 
 	read_info_alternates(get_object_directory(), 0);
 }