FwHeadless never clears untracked files, so settings a user deleted come back on every sync

A FLEx user's deletion of a settings file cannot stick. FwHeadless re-commits the file on its next sync, indefinitely.

Measured on one production project, where the same reversal-index configuration under CachedSettings/ConfigurationSettings/ReversalIndex/ went through three full cycles:

It is only UI configuration, so nothing was lost. But the loop is mechanical, it has run three times, and it will keep running.

Mechanism

FwHeadless's project directory is long-lived: it is the fwdata cache, and it survives between syncs. hg update never removes untracked files, so a copy of the file has been sitting in the working directory's ConfigurationSettings/ since it was first created, and no checkout will ever clear it.

FLExBridge then copies the settings folders into the tracked CachedSettings/ tree on every send/receive, and CachedSettings/ tracks files that ConfigurationSettings/ does not: several ReversalIndex/*.fwdictconfig files exist only under CachedSettings/ in that project's repository. So the stray gets committed through the cache each time, no matter how many times a user deletes it.

Same class of problem, not observed leaking yet: two WritingSystemStore/*.ldml files are also untracked in that directory. If those ever reach the cache, the container starts inventing writing systems for the project.

Why "purge untracked files" is the wrong fix

The untracked set in a real project directory:

fw.fwdata                             the project itself, reconstituted at checkout
fw.bak                                its backup
ConfigurationSettings/**              17 files, the actual leak
WritingSystemStore/*.ldml             2 files
SharedSettings/LexiconSettings.plsx

hg purge, or hg update -C with --clean semantics over the whole tree, deletes the project. Any fix has to name what it removes rather than removing what it does not recognise.

What needs deciding

A rule for which subtrees are project data, never touched, and which are container-local state that may be reconciled. Proposal to argue with:

• Reconcile ConfigurationSettings/ only. It is regenerable UI configuration and never holds lexical data.
• Delete a file there only when the tracked CachedSettings/ConfigurationSettings/ tree at the current revision does not contain it. That borrows FLExBridge's own idea of what belongs to the project instead of inventing a list we have to maintain.
• Do not touch the project root, LinkedFiles/, WritingSystemStore/ or SharedSettings/ in this pass. Flag the writing-system strays separately.
• Run it after checkout and before the pre-sync send/receive, so a stray never reaches the cache in the first place.

Tests

• a stray file dropped into ConfigurationSettings/ is absent from the commit the sync produces
• fw.fwdata, fw.bak, LinkedFiles/** and untracked WritingSystemStore/*.ldml all survive the reconcile
• a settings file that is tracked under CachedSettings/ is not deleted
• regression: a file deleted upstream and still present untracked locally does not reappear in the next commit

Notes

Found while auditing what the sync has written into fwdata across a project's full Mercurial history. It is the only thing the sync has re-added to a repository more than once, which is what makes it worth its own issue rather than a footnote.

Start by locating the FwHeadless checkout flow and the FLExBridge step that copies settings before pre-sync send/receive. Implement the proposed ConfigurationSettings reconciliation without touching the project root, LinkedFiles, WritingSystemStore or SharedSettings. Verify the listed stray-file, preservation, tracked-file, and deleted-upstream regression cases.