git-credential.txt: use list continuation

Use list continuation to avoid the second and third paragraphs
rendering with a different indentation from the first one where we
describe the "url" attribute.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-credential.txt

@@ -151,11 +151,11 @@ Git understands the following attributes:
 	were read (e.g., `url=https://example.com` would behave as if
 	`protocol=https` and `host=example.com` had been provided). This
 	can help callers avoid parsing URLs themselves.
-
-	Note that specifying a protocol is mandatory and if the URL
-	doesn't specify a hostname (e.g., "cert:///path/to/file") the
-	credential will contain a hostname attribute whose value is an
-	empty string.
-
-	Components which are missing from the URL (e.g., there is no
-	username in the example above) will be left unset.
++
+Note that specifying a protocol is mandatory and if the URL
+doesn't specify a hostname (e.g., "cert:///path/to/file") the
+credential will contain a hostname attribute whose value is an
+empty string.
++
+Components which are missing from the URL (e.g., there is no
+username in the example above) will be left unset.