Re-running a scan wipes the open comparison: the file view shows "Comparing repositories..." forever and Similar Repos goes empty

[matt-edmondson]

What's wrong

Both scans replace each GitRepository object in Options.Repos instead of updating the one already there:

• ScanDevDirectoryForOwnersAndRepos: Options.Repos[repoFullName] = gitHubRepo; (ProjectDirector/ProjectDirector.cs ~L1188)
• SyncGitHubRepoInfoForOwner: Options.Repos[repoName] = repo; (~L1020). This runs for "Scan > GitHub Owners" and for "Add New GitHub Owner".

The comparison state lives on the object: SimilarRepoDiffs and the requested/applied comparison tokens. The replacement has empty diffs and SimilarReposPending == false. Neither scan calls RefreshPage/UpdateSimilarRepos afterwards; they only call UpdateClonedStatus(). So after a rescan, until the user re-clicks the repo in the left list:

• Compare File view: FindDiff returns null, so ShowComparedFile shows the pending message ("Comparing repositories...") indefinitely, with nothing actually running.
• Compare Repo view: an empty file list.
• Similar Repos: an empty table.
• Propagate popup: offers no targets.

The new object also resets LastFetchTime to DateTime.MinValue, so every rescanned clone is fetched on the next tick. That adds to the burst described in #448.

Repro

In a scratch copy of the test project, using new ProjectDirector() with XDG dirs redirected and the private methods driven by reflection:

1. Create two local repos with origins https://github.com/acme/a and https://github.com/acme/b, both containing shared.txt.
2. Run Scan Dev Dir, then SwitchPage("acme/a"), then wait for the comparison and select the compared repo and file.
3. Run Scan Dev Dir again.

before scan: diff found=True
after scan:  same object=False pending=False diff found=False siblings=0 lastFetch=01/01/0001 00:00:00

Suggested fix / acceptance criteria

• In both scans, when Options.Repos already contains the key, update the existing object in place: RemotePath, LocalPath, OwnerName and RepoName. That keeps its comparison and LastFetchTime.
• At a minimum, call RefreshPage() when a scan finishes.
• Acceptance: rescanning (Dev Dir or GitHub Owners) while a repo or file comparison is open either keeps it displayed or shows a real pending state that resolves.

This is distinct from #438. Its open fix, PR #473, preserves LocalPath but still assigns a new object, so it doesn't address this; the two would fit naturally in one change.

[matt-edmondson]

Triage

• Category: Bug
• Priority: Medium. After a rescan the comparison views show stale or empty state ("Comparing repositories..." forever) until the user re-selects the repo. No data is lost, but the UI is misleading, and the reset LastFetchTime adds to the fetch burst in Auto-fetch starts a git fetch for every cloned repository at the same moment every minute, with no concurrency limit and no in-flight check #448.
• Area / suggested assignment: Scanning and repo model (ScanDevDirectoryForOwnersAndRepos, SyncGitHubRepoInfoForOwner).
• Duplicates / related: Related to After "Scan GitHub Owners", repos found by "Scan Dev Dir" point at a nonexistent folder, fail a fetch every minute, and show broken Pull/Commit/Push #438 and Auto-fetch starts a git fetch for every cloned repository at the same moment every minute, with no concurrency limit and no in-flight check #448.
• In progress: PR Keep a cloned repository's folder when an owner scan lists it [patch] #473 ("Keep a cloned repository's folder when an owner scan lists it") touches the same assignment sites but still replaces the object, so it does not fix this. Updating the existing object in place could be folded into Keep a cloned repository's folder when an owner scan lists it [patch] #473 or follow straight after it.

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