scap has a lot of machinery involved with converting CDB files to JSON and avoiding the CDB files when rsyncing between hosts, and reconstituting the CDB files from the JSON files on target hosts. I wonder if this is still useful/necessary.
Related context:
* {T221428}
* {T99740}
rsync stats comparison between rsync_cdbs:True and rsync_cdbs:False when altering a set of l10n files (https://gerrit.wikimedia.org/r/c/mediawiki/core/+/749100). The commit results in 13 of 449 CDB files being updated. The following are stats from rsync when pulling to a target host during `scap sync-world`
```name=rsync_cdbs:True
Number of files: 263,633 (reg: 243,594, dir: 19,871, link: 168)
Number of created files: 1 (reg: 1)
Number of deleted files: 0
Number of regular files transferred: 27
Total file size: 6,855,911,866 bytes
Total transferred file size: 68,003,603 bytes
Literal data: 7,253,928 bytes <---
Matched data: 60,749,675 bytes <---
File list size: 6,750,842
File list generation time: 1.037 seconds
File list transfer time: 0.000 seconds
Total bytes sent: 199,009
Total bytes received: 9,751,864
```
```name=rsync_cdbs:False
Number of files: 264,530 (reg: 244,489, dir: 19,873, link: 168)
Number of created files: 1 (reg: 1)
Number of deleted files: 0
Number of regular files transferred: 40
Total file size: 7,141,639,029 bytes
Total transferred file size: 69,132,414 bytes
Literal data: 2,187,974 bytes <---
Matched data: 66,944,440 bytes <---
File list size: 6,779,014
File list generation time: 1.033 seconds
File list transfer time: 0.000 seconds
Total bytes sent: 200,277
Total bytes received: 7,225,108
```
This confirms that changes to the JSON files rsync better than their CDB counterparts. An open question is if the better rsync efficiency is more important than the code and operational complexity.