[tex-live] no backups kept

[jfbu]

Hi,

I wanted to test the backups functionality, and something strange happens: upon removing collection-context, no backups at all have been done.

$ tlmgr option show
Number of backups to keep (autobackup): 1
Directory for backups (backupdir): tlpkg/backups
Create formats on installation (formats): 1
Run tlmgr generate updmap after maps have changed (generate_updmap): 0
Install documentation files (docfiles): 1
Install source files (srcfiles): 1
Default package repository (repository): /Users/jfb/Downloads/TLmirror/
Run postinst code blobs (postcode): 1
Destination for symlinks for binaries (sys_bin): /usr/local/bin
Destination for symlinks for info docs (sys_info): /usr/local/share/info
Destination for symlinks for man pages (sys_man): /usr/local/share/man

$ tlmgr info collections
tlmgr: package repository /Users/jfb/Downloads/TLmirror (verified)
i collection-basic: Essential programs and files
  collection-bibtexextra: BibTeX additional styles
i collection-binextra: TeX auxiliary programs
i collection-context: ConTeXt and packages
i collection-fontsextra: Additional fonts
i ...

$ tlmgr remove collection-context
tlmgr: not removing collection-context, needed by scheme-context
tlmgr: no packages removed.
tlmgr: action remove returned an error; continuing.
tlmgr: An error has occurred. See above messages. Exiting.

$ tlmgr remove scheme-context
tlmgr: removing collection-context
tlmgr: removing collection-metapost
tlmgr: removing package automata
...
tlmgr: ultimately removed these packages: automata bbcard blockdraw_mp bpolynomial cmarrows collection-context collection-metapost context context-account context-algorithmic context-animation context-annotation context-bnf context-chromato context-cmscbf context-cmttbf context-construction-plan context-cyrillicnumbers context-degrade context-fancybreak context-filter context-french context-fullpage context-gantt context-gnuplot context-inifile context-layout context-letter context-lettrine context-mathsets context-notes-zh-cn context-rst context-ruby context-simplefonts context-simpleslides context-title context-transliterator context-typearea context-typescripts context-vim context-visualcounter context.x86_64-darwinlegacy drv dviincl emp epsincl expressg exteps featpost feynmf feynmp-auto garrigues gmp hatching jmn latexmp mcf2graph metago metaobj metaplot metapost metapost.x86_64-darwinlegacy metauml mfpic mfpic4ode mp3d mparrows mpattern mpcolornames mpgraphics piechartmp repere roex roundrect scheme-context shapes slideshow splines suanpan textpath threeddice
running mktexlsr ...
done running mktexlsr.
running updmap-sys ...
done running updmap-sys.
regenerating fmtutil.cnf in /usr/local/texlive/2017/texmf-dist
tlmgr: package log updated: /usr/local/texlive/2017/texmf-var/web2c/tlmgr.log

$ du -hc -d0 /usr/local/texlive/2017/tlpkg/backups
  0B	/usr/local/texlive/2017/tlpkg/backups
  0B	total

??

Best,

Jean-François