Some doc improvements

include/git2/transport.h

@@ -45,10 +45,12 @@ typedef struct git_cred_userpass_plaintext {
 
 /**
  * Creates a new plain-text username and password credential object.
+ * The supplied credential parameter will be internally duplicated.
  *
  * @param out The newly created credential object.
  * @param username The username of the credential.
  * @param password The password of the credential.
+ * @return 0 for success or an error code for failure
  */
 GIT_EXTERN(int) git_cred_userpass_plaintext_new(
 	git_cred **out,
@@ -62,6 +64,7 @@ GIT_EXTERN(int) git_cred_userpass_plaintext_new(
  * @param url The resource for which we are demanding a credential.
  * @param allowed_types A bitmask stating which cred types are OK to return.
  * @param payload The payload provided when specifying this callback.
+ * @return 0 for success or an error code for failure
  */
 typedef int (*git_cred_acquire_cb)(
 	git_cred **cred,