Improve SSH button tooltips for better usability (#1369)

* Requires new translations before the next release
* Fix a typo in "backup-job" command description

Co-authored-by: aryoda <11374410+aryoda@users.noreply.github.com>

common/backintime.py

@@ -239,7 +239,7 @@ def createParsers(app_name = 'backintime'):
     aliases.append((command, nargs))
     description = 'Take a new snapshot in background only '      +\
                   'if the profile is scheduled and the machine ' +\
-                  'is not on battery. This is use by cron jobs.'
+                  'is not on battery. This is used by cron jobs.'
     backupJobCP =          subparsers.add_parser(command,
                                                  parents = [rsyncArgsParser],
                                                  epilog = epilogCommon,

qt/settingsdialog.py

@@ -245,7 +245,7 @@ def __init__(self, parent):
         self.btnSshPrivateKeyFile = QToolButton(self)
         self.btnSshPrivateKeyFile.setToolButtonStyle(Qt.ToolButtonIconOnly)
         self.btnSshPrivateKeyFile.setIcon(icon.FOLDER)
-        self.btnSshPrivateKeyFile.setToolTip(_('Key File'))
+        self.btnSshPrivateKeyFile.setToolTip(_('Choose an existing private key file (normally named "id_rsa")'))
         self.btnSshPrivateKeyFile.setMinimumSize(32, 28)
         hlayout3.addWidget(self.btnSshPrivateKeyFile)
         self.btnSshPrivateKeyFile.clicked \
@@ -255,10 +255,11 @@ def __init__(self, parent):
         self.btnSshKeyGen.setToolButtonStyle(Qt.ToolButtonIconOnly)
         self.btnSshKeyGen.setIcon(icon.ADD)
         self.btnSshKeyGen.setToolTip(
-            _('Create a new SSH key without Password.'))
+            _('Create a new SSH key without password (not allowed if a private key file is already selected)'))
         self.btnSshKeyGen.setMinimumSize(32, 28)
         hlayout3.addWidget(self.btnSshKeyGen)
         self.btnSshKeyGen.clicked.connect(self.btnSshKeyGenClicked)
+        # Disable SSH key generation button if a key file is already set
         self.txtSshPrivateKeyFile.textChanged \
             .connect(lambda x: self.btnSshKeyGen.setEnabled(not x))