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What Happens When You Remove A File

When you remove a file from a project, it doesn't just disappear. CVS must be able to retrieve such files when you request an old snapshot of the project. Instead, the file gets put in the Attic, literally:

     floss$ pwd
     /home/jrandom/src/myproj
     floss$ ls /usr/local/newrepos/myproj/
     README.txt,v  a-subdir/     b-subdir/     foo.jpg,v   hello.c,v
     floss$ rm foo.jpg
     floss$ cvs rm foo.jpg
     cvs remove: scheduling 'foo.jpg' for removal
     cvs remove: use 'cvs commit' to remove this file permanently
     floss$ cvs ci -m "Removed foo.jpg" foo.jpg
     Removing foo.jpg;
     /usr/local/newrepos/myproj/foo.jpg,v  <--  foo.jpg
     new revision: delete; previous revision: 1.1
     done
     floss$ cd /usr/local/newrepos/myproj/
     floss$ ls
     Attic/      README.txt,v  a-subdir/     b-subdir/   hello.c,v
     floss$ cd Attic
     floss$ ls
     foo.jpg,v
     floss$

In each repository directory of a project, the presence of an Attic/ subdirectory means that at least one file has been removed from that directory (this means that you shouldn't use directories named Attic in your projects). CVS doesn't merely move the RCS file into Attic/, however; it also commits a new revision into the file, with a special revision state of dead. Here's the relevant section from Attic/foo.jpg,v:

     1.2
     date   99.06.21.03.38.07;   author jrandom;   state dead;
     branches;
     next	1.1;

If the file is later brought back to life, CVS has a way of recording that it was dead at some point in the past and is now alive again.

This means that if you want to restore a removed file, you can't just take it out of the Attic/ and put it back into the project. Instead, you have to do something like this in a working copy:

     floss$ pwd
     /home/jrandom/src/myproj
     floss$ cvs -Q update -p -r 1.1 foo.jpg > foo.jpg
     floss$ ls
     CVS/       README.txt   a-subdir/   b-subdir/   foo.jpg     hello.c
     floss$ cvs add -kb foo.jpg
     cvs add: re-adding file foo.jpg (in place of dead revision 1.2)
     cvs add: use 'cvs commit' to add this file permanently
     floss$ cvs ci -m "revived jpg image" foo.jpg
     Checking in foo.jpg;
     /usr/local/newrepos/myproj/foo.jpg,v  <-- foo.jpg
     new revision: 1.3; previous revision: 1.2
     done
     floss$ cd /usr/local/newrepos/myproj/
     floss$ ls
     Attic/	      a-subdir/     foo.jpg,v
     README.txt,v  b-subdir/     hello.c,v
     floss$ ls Attic/
     floss$

There's a lot more to know about RCS format, but this is sufficient for a CVS adminstrator to maintain a repository. It's quite rare to actually edit an RCS file; you'll usually just have to tweak file permissions in the repository, at least if my own experience is any guide. Nevertheless, when CVS starts behaving truly weirdly (rare, but not completely outside the realm of possibility), you may want to actually look inside the RCS files to figure out what's going on.

Karl Fogel wrote this book. Buy a printed copy via his homepage at red-bean.com

copyright  ©  March 25 2019 sean dreilinger url: https://durak.org/sean/pubs/software/cvsbook/What-Happens-When-You-Remove-A-File.html