Multiple changes.

- Add build manifests for SourceHut.
  - Update README destination links.
  - Fix manifest for prerelease gem.
  - Reopen env handles when #clear is successful.
  - Fix #each when there is only one key.
  - Always use io_vec lengths when creating new strings.
  - Hook for rdoc generation.
  - Rename #open to #reopen, don't alias it.
  - Add a Rollback exception for upcoming transaction block work

FossilOrigin-Name: d6ddedc51b0ac67f395d5749aa3e6adbeebdaf2843c6402ace757b0afffc2be9

README.md

@@ -1,21 +1,22 @@
 # Ruby MDBX
 
 home
-: https://gitlab.com/mahlon/ruby-mdbx
+: https://code.martini.nu/ruby-mdbx
 
 code
 : https://code.martini.nu/ruby-mdbx
 
+docs
+: https://martini.nu/docs/ruby-mdbx
+
 github
 : https://github.com/mahlon/ruby-mdbx
 
 gitlab
-: https://gitlab.com/mahlon/ruby-mdbx/-/tree-master
+: https://gitlab.com/mahlon/ruby-mdbx
 
-
-docs
-: https://martini.nu/docs/ruby-mdbx
-#FIXME: ....... somewhere on martini
+sourcehut:
+: https://hg.sr.ht/~mahlon/ruby-mdbx
 
 
 ## Description