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, 40 insertions, 0 deletions

diff --git a/modules/setting/directory.go b/modules/setting/directory.go
new file mode 100644
index 0000000000..5dcdd89c04
--- /dev/null
+++ b/modules/setting/directory.go
@@ -0,0 +1,40 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package setting
+
+import (
+	"fmt"
+	"os"
+)
+
+// PrepareAppDataPath creates app data directory if necessary
+func PrepareAppDataPath() error {
+	// FIXME: There are too many calls to MkdirAll in old code. It is incorrect.
+	// For example, if someDir=/mnt/vol1/gitea-home/data, if the mount point /mnt/vol1 is not mounted when Gitea runs,
+	// then gitea will make new empty directories in /mnt/vol1, all are stored in the root filesystem.
+	// The correct behavior should be: creating parent directories is end users' duty. We only create sub-directories in existing parent directories.
+	// For quickstart, the parent directories should be created automatically for first startup (eg: a flag or a check of INSTALL_LOCK).
+	// Now we can take the first step to do correctly (using Mkdir) in other packages, and prepare the AppDataPath here, then make a refactor in future.
+
+	st, err := os.Stat(AppDataPath)
+
+	if os.IsNotExist(err) {
+		err = os.MkdirAll(AppDataPath, os.ModePerm)
+		if err != nil {
+			return fmt.Errorf("unable to create the APP_DATA_PATH directory: %q, Error: %v", AppDataPath, err)
+		}
+		return nil
+	}
+
+	if err != nil {
+		return fmt.Errorf("unable to use APP_DATA_PATH %q. Error: %v", AppDataPath, err)
+	}
+
+	if !st.IsDir() /* also works for symlink */ {
+		return fmt.Errorf("the APP_DATA_PATH %q is not a directory (or symlink to a directory) and can't be used", AppDataPath)
+	}
+
+	return nil
+}