When patchname exists, cdbs-edit-patch will set up a temporary working source tree, apply all patches up to and including patchname in lexicographic order, and spawn an interactive shell for the developer. The developer can then edit files in this working tree. When the developer is done and exits the shell, cdbs-edit-patch updates patchname to reflect the changes made. To abort the process from the interactive shell, exit with a nonzero exit value.
When patchname does not exist, cdbs-edit-patch will assume that a new patch should be created. As with the above scenario, cdbs-edit-patch will first create a temporary working source tree and apply all patches up to the new patch in lexicographic order. When the shell is quit, cdbs-edit-patch will create patchname.