a file map can be:
- created internally inside chunkify by calling sparsemap, which uses
SEEK_DATA / SEEK_HOLE to determine data and hole ranges inside a
seekable sparse file.
Usage: borg create --sparse --chunker-params=fixed,BLOCKSIZE ...
BLOCKSIZE is the chunker blocksize here, not the filesystem blocksize!
- made by some other means and given to the chunkify function.
this is not used yet, but in future this could be used to only read
the changed parts and seek over the (known) unchanged parts of a file.
sparsemap: the generate range sizes are multiples of the fs block size.
the tests assume 4kiB fs block size.
add a push-style example to borg-create docs
When I browsed the readthedocs and manpages while setting up Borg for
myself for the first time, I saw multiple hints that pushing backups via
SSH is supported (e.g. the existence of the `borg serve` command and the
`--rsh` option), but I never found a clear example. I only found
<https://borgbackup.readthedocs.io/en/stable/usage/general.html#repository-urls>
after being pointed to it by @ThomasWaldmann.
Therefore, an explicit example in the `borg create` documentation seems
appropriate. I put it next to the pull-style example using sshfs which
serves a similar usecase.
