The --remove-source-files destroys data when source & destination are the same (data loss!)

[samueloph]

Hello,

I'm forwarding this bug report I've received on Debian:
https://bugs.debian.org/1016102

I'm verbatim copying the report below:

I accidentally ran:

  $ rsync -va --progress --remove-source-files "$dir_with_many_files" "$dir_with_many_files"

Due to a typo when using bash history substitution, the source and
destination were both directories and they both named the same
directory.

The expectation is that rsync should detect movement from A to A and
do nothing apart from warning the user that there is nothing to do.
Instead, because of the “--remove-source-files” option, rsync DESTROYS
all the files in "$dir_with_many_files" irrevokably.

There needs to be a safeguard that prevents --remove-source-files from
having effect if:

 * Files are not copied to the destination (for any reason)
 * The source and destination are the same

I suffered data loss because of this.  At the very least, if it’s
really intended for “rsync --remove-source-files $A $A” to effectively
behave like “rm -rf $A/*”, there AT LEAST needs to be a very loud
warning prompting the user for confirmation. But I conjecture that there
never is a legit scenario where “rsync --remove-source-files” simply
destroys files without safely ensuring they exist somewhere in the
end.

The issue can be reproduced with:

mkdir testdir-remove-source-files-1016102 && touch testdir-remove-source-files-1016102/file-a && touch testdir-remove-source-files-1016102/file-b
ls testdir-remove-source-files-1016102
rsync -va --progress --remove-source-files testdir-remove-source-files-1016102/ testdir-remove-source-files-1016102/
ls testdir-remove-source-files-1016102

[WayneD]

Duplicate of #304.