compat/terminal: support echoing on windows

Without /dev/tty support, git_terminal_prompt simply ignores the
'echo'-parameter. On Windows we can do better by clevering up our
getpass-implementation a bit so it can conditionally echo.

While we're at it, plug a small memory-leak by returning a pointer
to a static strbuf instead of detaching it. This is the same thing
the /dev/tty-version of git_terminal_prompt does, and the callee
doesn't expect to have to free it's memory.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>

compat/mingw.c

@@ -1850,21 +1850,6 @@ int link(const char *oldpath, const char *newpath)
 	return 0;
 }
 
-char *getpass(const char *prompt)
-{
-	struct strbuf buf = STRBUF_INIT;
-
-	fputs(prompt, stderr);
-	for (;;) {
-		char c = _getch();
-		if (c == '\r' || c == '\n')
-			break;
-		strbuf_addch(&buf, c);
-	}
-	fputs("\n", stderr);
-	return strbuf_detach(&buf, NULL);
-}
-
 pid_t waitpid(pid_t pid, int *status, int options)
 {
 	HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,

compat/mingw.h

@@ -56,8 +56,6 @@ struct passwd {
 	char *pw_dir;
 };
 
-extern char *getpass(const char *prompt);
-
 typedef void (__cdecl *sig_handler_t)(int);
 struct sigaction {
 	sig_handler_t sa_handler;

compat/terminal.c

@@ -71,6 +71,26 @@ char *git_terminal_prompt(const char *prompt, int echo)
 	return buf.buf;
 }
 
+#elif defined(WIN32)
+
+char *git_terminal_prompt(const char *prompt, int echo)
+{
+	static struct strbuf buf = STRBUF_INIT;
+
+	fputs(prompt, stderr);
+	strbuf_reset(&buf);
+	for (;;) {
+		int c = _getch();
+		if (c == '\n' || c == '\r')
+			break;
+		if (echo)
+			putc(c, stderr);
+		strbuf_addch(&buf, c);
+	}
+	putc('\n', stderr);
+	return buf.buf;
+}
+
 #else
 
 char *git_terminal_prompt(const char *prompt, int echo)