Merge 'unmask-credentials-username'

This came in via pull request #677 from yaras/fix-git-675

Fixed masking username with asterisks when reading credentials

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

credential.c

@@ -136,7 +136,9 @@ static void credential_getpass(struct credential *c)
 {
 	if (!c->username)
 		c->username = credential_ask_one("Username", c,
-						 PROMPT_ASKPASS|PROMPT_ECHO);
+						 (getenv("GIT_ASKPASS") ?
+						  PROMPT_ASKPASS : 0) |
+						 PROMPT_ECHO);
 	if (!c->password)
 		c->password = credential_ask_one("Password", c,
 						 PROMPT_ASKPASS);