git-annex/doc/walkthrough/automatically_managing_content.mdwn

Once you have multiple repositories, and have perhaps configured numcopies,
any given file can have many more copies than is needed, or perhaps fewer
than you would like. How to manage this?

The whereis subcommand can be used to see how many copies of a file are known,
but then you have to decide what to get or drop. In this example, there
are rather too many copies of `other_file` and perhaps not enough of the
other file.

	# cd /media/usbdrive
	# git annex whereis
	whereis my_cool_big_file (1 copy)
		0c443de8-e644-11df-acbf-f7cd7ca6210d  -- laptop
	whereis other_file (3 copies)
		0c443de8-e644-11df-acbf-f7cd7ca6210d  -- laptop
		62b39bbe-4149-11e0-af01-bb89245a1e61  -- usb drive <-- here
		7570b02e-15e9-11e0-adf0-9f3f94cb2eaa  -- backup drive

What would be handy is some automated versions of get and drop, that only
get a file if there are not yet enough copies of it, or only drop a file
if there are too many copies. Well, these exist, just use the --auto
option.

	# git annex get --auto --numcopies=2
	get my_cool_big_file (from laptop...) ok
	# git annex drop --auto --numcopies=2
	drop other_file ok

With two quick commands, git-annex was able to decide for you how to
work toward having two copies of your files.

	# git annex whereis
	whereis my_cool_big_file (2 copies)
		0c443de8-e644-11df-acbf-f7cd7ca6210d  -- laptop
		62b39bbe-4149-11e0-af01-bb89245a1e61  -- usb drive <-- here
	whereis other_file (2 copies)
		0c443de8-e644-11df-acbf-f7cd7ca6210d  -- laptop
		7570b02e-15e9-11e0-adf0-9f3f94cb2eaa  -- backup drive

The --auto option can also be used with the copy command,
again this lets git-annex decide whether to actually copy content.
remove optimize subcommand; use --auto instead get, drop: Added --auto option, which decides whether to get/drop content as needed to work toward the configured numcopies. The problem with bundling it up in optimize was that I then found I wanted to run an optmize that did not drop files, only got them. Considered adding a --only-get switch to it, but that seemed wrong. Instead, let's make existing subcommands optionally smarter. Note that the only actual difference between drop and drop --auto is that the latter does not even try to drop a file if it knows of not enough copies, and does not print any error messages about files it was unable to drop. It might be nice to make get avoid asking git for attributes when not in auto mode. For now it always asks for attributes. 2011-09-15 17:30:04 +00:00			`Once you have multiple repositories, and have perhaps configured numcopies,`
			`any given file can have many more copies than is needed, or perhaps fewer`
			`than you would like. How to manage this?`

			`The whereis subcommand can be used to see how many copies of a file are known,`
			`but then you have to decide what to get or drop. In this example, there`
			are rather too many copies of `other_file` and perhaps not enough of the
			`other file.`

			`# cd /media/usbdrive`
			`# git annex whereis`
			`whereis my_cool_big_file (1 copy)`
			`0c443de8-e644-11df-acbf-f7cd7ca6210d -- laptop`
			`whereis other_file (3 copies)`
			`0c443de8-e644-11df-acbf-f7cd7ca6210d -- laptop`
			`62b39bbe-4149-11e0-af01-bb89245a1e61 -- usb drive <-- here`
			`7570b02e-15e9-11e0-adf0-9f3f94cb2eaa -- backup drive`

			`What would be handy is some automated versions of get and drop, that only`
			`get a file if there are not yet enough copies of it, or only drop a file`
			`if there are too many copies. Well, these exist, just use the --auto`
			`option.`

			`# git annex get --auto --numcopies=2`
			`get my_cool_big_file (from laptop...) ok`
			`# git annex drop --auto --numcopies=2`
			`drop other_file ok`

			`With two quick commands, git-annex was able to decide for you how to`
			`work toward having two copies of your files.`

			`# git annex whereis`
			`whereis my_cool_big_file (2 copies)`
			`0c443de8-e644-11df-acbf-f7cd7ca6210d -- laptop`
			`62b39bbe-4149-11e0-af01-bb89245a1e61 -- usb drive <-- here`
			`whereis other_file (2 copies)`
			`0c443de8-e644-11df-acbf-f7cd7ca6210d -- laptop`
			`7570b02e-15e9-11e0-adf0-9f3f94cb2eaa -- backup drive`
copy --auto Only does copy when numcopies is not yet satisfied. 2011-09-15 19:27:45 +00:00
			`The --auto option can also be used with the copy command,`
			`again this lets git-annex decide whether to actually copy content.`