feat(root): refactor root access

[researchxxl]

• restore outdated and buggy old root code
• migrate settings screen to kotlin
• use a maintained libsuperuser dependency instead of the old unmaintained one
• add code conflict detection works with root

[vale981]

Currently running the debug build :). Can confirm that this works. Thanks :)

[vale981]

Currently the "Run Script" feature does not work as the scripts ion ".stfolder" are likely not accessible due to permission issues. Would it be possible to fix this?

[researchxxl]

@vale981

Currently the "Run Script" feature does not work as the scripts ion ".stfolder" are likely not accessible due to permission issues. Would it be possible to fix this?

pls look at util.runScriptSet and runShellCommandGetOutput(command, false).. if you set true you will get root exec of the scripts

needs secure and proper implementation tbh for being accepted here and file permissions should be checked before

[researchxxl]

@dbhavsar76 may i kindly ask if you like to have fun with this?? it is also ok for me if you dont take the challenge

[dbhavsar76]

I'll see what i can do. No promises. Meanwhile, I have the drawer ready.

[Copilot]

Pull request overview

This PR refactors the app’s “run Syncthing as root” support by introducing a root capability check, adding a user-facing root toggle in settings, and updating service/runtime behavior to execute process management and permission-repair steps with root where appropriate.

Changes:

• Add RootAccess helper and a new “Run Syncthing as Superuser” preference, wiring it into the settings UI and runtime startup logic.
• Adjust shell-command helpers and Syncthing process management to optionally execute via su, including environment setup when launching Syncthing under root.
• Attempt to repair app data permissions/SELinux contexts when config read/write fails (to recover from prior root-owned files).

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
gradle/libs.versions.toml	Adds libsuperuser version + catalog entry for root availability checks.
app/build.gradle.kts	Adds the libsuperuser dependency to the app module.
app/src/main/res/values/strings.xml	Adds user-facing strings for root toggle + root denial toast.
app/src/main/java/com/nutomic/syncthingandroid/util/Util.java	Adds permission-fix helper and root-capable shell execution helpers.
app/src/main/java/com/nutomic/syncthingandroid/util/ConfigXml.java	Attempts permission repair before failing config parse/save due to access issues.
app/src/main/java/com/nutomic/syncthingandroid/settings/SettingsBehaviorScreen.kt	Adds UI switch to enable/disable root mode and restarts service on change.
app/src/main/java/com/nutomic/syncthingandroid/service/SyncthingService.java	Stops treating use_root as deprecated during pref import.
app/src/main/java/com/nutomic/syncthingandroid/service/SyncthingRunnable.java	Runs process discovery/kill and syncthing launch via root when enabled.
app/src/main/java/com/nutomic/syncthingandroid/service/Constants.java	Introduces PREF_USE_ROOT constant.
app/src/main/java/com/nutomic/syncthingandroid/root/RootAccess.java	New helper for blocking root availability check via libsuperuser.
app/src/main/java/com/nutomic/syncthingandroid/receiver/BootReceiver.java	Kills leftover SyncthingNative after app update when running in root mode.

Suppressed comments (1)

app/src/main/java/com/nutomic/syncthingandroid/util/ConfigXml.java:1267

• Same pattern as in parseConfig(): after attempting fixAppDataPermissions(), re-check writability before proceeding, otherwise the method may continue and fail later when trying to write the temp file/rename, while the log suggests the permission issue was handled.

        if (!mConfigFile.canWrite() && !Util.fixAppDataPermissions(mContext)) {
            Log.w(TAG, "Failed to save updated config. Cannot change the owner of the config file.");
            return;
        }