Define GIT_(AUTHOR|COMMITTER)_(NAME|EMAIL) to known values.

Without these, running tests with an account with empty gecos
field would fail.

We might want to loosen error from "git-var -l" (but not
"git-var GIT_AUTHOR_NAME") later, but that is more or less an
independent issue.

Signed-off-by: Junio C Hamano <junkio@cox.net>

t/test-lib.sh

@@ -16,11 +16,11 @@ unset COMMIT_AUTHOR_EMAIL
 unset COMMIT_AUTHOR_NAME
 unset GIT_ALTERNATE_OBJECT_DIRECTORIES
 unset GIT_AUTHOR_DATE
-unset GIT_AUTHOR_EMAIL
-unset GIT_AUTHOR_NAME
+GIT_AUTHOR_EMAIL=author@example.com
+GIT_AUTHOR_NAME='A U Thor'
 unset GIT_COMMITTER_DATE
-unset GIT_COMMITTER_EMAIL
-unset GIT_COMMITTER_NAME
+GIT_COMMITTER_EMAIL=committer@example.com
+GIT_COMMITTER_NAME='C O Mitter'
 unset GIT_DIFF_OPTS
 unset GIT_DIR
 unset GIT_EXTERNAL_DIFF
@@ -28,6 +28,8 @@ unset GIT_INDEX_FILE
 unset GIT_OBJECT_DIRECTORY
 unset SHA1_FILE_DIRECTORIES
 unset SHA1_FILE_DIRECTORY
+export GIT_AUTHOR_EMAIL GIT_AUTHOR_NAME
+export GIT_COMMITTER_EMAIL GIT_COMMITTER_NAME
 
 # Each test should start with something like this, after copyright notices:
 #