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+git-annex keeps track of in which repositories it last saw a file's content.
+This location tracking information is stored in `.git-annex/$key.log`.
+Repositories record their UUID and the date when they get or drop 
+a file's content. (Git is configured to use a union merge for this file,
+so the lines may be in arbitrary order, but it will never conflict.)
+
+This location tracking information is useful if you have multiple
+repositories, and not all are always accessible. For example, perhaps one
+is on a home file server, and you are away from home. Then git-annex can
+tell you what git remote it needs access to in order to get a file:
+
+	# git annex get myfile 
+	get myfile(not available)
+	  I was unable to access these remotes: home
+
+Another way the location tracking comes in handy is if you put repositories
+on removable USB drives, that might be archived away offline in a safe
+place. In this sort of case, you probably don't have a git remotes
+configured for every USB drive. So git-annex may have to resort to talking
+about repository UUIDs. If you have previously used "git annex init"
+to attach descriptions to those repositories, it will include their
+descriptions to help you with finding them:
+
+	# git annex get myfile
+	get myfile (not available)
+	  Try making some of these repositories available:
+	  	c0a28e06-d7ef-11df-885c-775af44f8882  -- USB archive drive 1
+	  	e1938fee-d95b-11df-96cc-002170d25c55