configure: add settings for gitconfig, editor and pager

Use the new GIT_PARSE_WITH_SET_MAKE_VAR macro to allow configuration
settings for ETC_GITCONFIG, DEFAULT_PAGER and DEFAULT_EDITOR.
Signed-off-by: NBen Walton <bwalton@artsci.utoronto.ca>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

configure.ac

@@ -246,6 +246,29 @@ GIT_PARSE_WITH(iconv))
 # Define USE_STDEV below if you want git to care about the underlying device
 # change being considered an inode change from the update-index perspective.
 
+#
+# Allow user to set ETC_GITCONFIG variable
+GIT_PARSE_WITH_SET_MAKE_VAR(gitconfig, ETC_GITCONFIG,
+			Use VALUE instead of /etc/gitconfig as the
+			global git configuration file.
+			If VALUE is not fully qualified it will be interpretted
+			as a path relative to the computed prefix at runtime.)
+
+#
+# Allow user to set the default pager
+GIT_PARSE_WITH_SET_MAKE_VAR(pager, DEFAULT_PAGER,
+			Use VALUE as the fall-back pager instead of 'less'.
+			This is used by things like 'git log' when the user
+			does not specify a pager to use through alternate
+			methods. eg: /usr/bin/pager)
+#
+# Allow user to set the default editor
+GIT_PARSE_WITH_SET_MAKE_VAR(editor, DEFAULT_EDITOR,
+			Use VALUE as the fall-back editor instead of 'vi'.
+			This is used by things like 'git commit' when the user
+			does not specify a preferred editor through other
+			methods. eg: /usr/bin/editor)
+
 #
 # Define SHELL_PATH to provide path to shell.
 GIT_ARG_SET_PATH(shell)