gpg: Implement --dry-run for --passwd.

* g10/keyedit.c (change_passphrase): Take care of --dry-run.

Signed-off-by: Werner Koch <wk@gnupg.org>

doc/gpg.texi

@@ -1126,7 +1126,9 @@ all affected self-signatures is set one second ahead.
 @opindex passwd
 Change the passphrase of the secret key belonging to the certificate
 specified as @var{user-id}.  This is a shortcut for the sub-command
-@code{passwd} of the edit key menu.
+@code{passwd} of the edit key menu.  When using together with the
+option @option{--dry-run} this will not actually change the passphrase
+but check that the current passphrase is correct.
 
 @end table
 

g10/keyedit.c

@@ -1134,8 +1134,10 @@ change_passphrase (ctrl_t ctrl, kbnode_t keyblock)
           if (err)
             goto leave;
 
+          /* Note that when using --dry-run we don't change the
+           * passphrase but merely verify the current passphrase.  */
           desc = gpg_format_keydesc (ctrl, pk, FORMAT_KEYDESC_NORMAL, 1);
-          err = agent_passwd (ctrl, hexgrip, desc, 0,
+          err = agent_passwd (ctrl, hexgrip, desc, !!opt.dry_run,
                               &cache_nonce, &passwd_nonce);
           xfree (desc);