Improve install code to avoid low-level mistakes. (#17779)

* Improve install code to avoid low-level mistakes.

If a user tries to do a re-install in a Gitea database, they gets a warning and double check.
When Gitea runs, it never create empty app.ini automatically.

Also some small (related) refactoring:

* Refactor db.InitEngine related logic make it more clean (especially for the install code)
* Move some i18n strings out from setting.go to make the setting.go can be easily maintained.
* Show errors in CLI code if an incorrect app.ini is used.
* APP_DATA_PATH is created when installing, and checked when starting (no empty directory is created any more).

1 files changed, 22 insertions, 9 deletions

diff --git a/web_src/less/_install.less b/web_src/less/_install.less
index 3f59a99aac..c6d93c514c 100644
--- a/web_src/less/_install.less
+++ b/web_src/less/_install.less
@@ -4,7 +4,7 @@
   form {
     @input-padding: 320px !important;
 
-    label {
+    .inline.field label {
       text-align: right;
       width: @input-padding;
     }
@@ -20,19 +20,32 @@
         margin-left: @input-padding+15px;
       }
 
-      &.optional .title {
-        margin-left: 38%;
+      &.optional {
+        .title {
+          margin-left: 38%;
+        }
+        .checkbox {
+          margin-left: 40% !important;
+          label {
+            width: auto !important;
+          }
+        }
       }
     }
   }
 
   .ui {
-    .checkbox {
-      margin-left: 40% !important;
-
-      label {
-        width: auto !important;
-      }
+    .reinstall-message {
+      width: 70%;
+      margin: 20px auto;
+      color: red;
+      text-align: left;
+      font-weight: bold;
+    }
+    .reinstall-confirm {
+      width: 70%;
+      text-align: left;
+      margin: 10px auto;
     }
   }
 }