rename.1: document edge cases.

Document the behaviour of an empty `expression` argument, and of `/` in
the `expression` and `replacement` arguments.

I also tried to make it slightly clearer that `-s` changes where a
symlink points, but doesn't change the thing that it points at.

diff --git a/misc-utils/rename.1.adoc b/misc-utils/rename.1.adoc
index 5eb1959573ccfcdf8208acd83926eb8f3c18fccb..11518e94cf9af6ab58b9007c63cc2e0be884272e 100644 (file)
--- a/misc-utils/rename.1.adoc
+++ b/misc-utils/rename.1.adoc
@@ -23,7 +23,7 @@ rename - rename files
 == OPTIONS
 
 *-s*, *--symlink*::
-Do not rename a symlink but its target.
+Do not rename a symlink but change where it points.
 
 *-v*, *--verbose*::
 Show which files were renamed, if any.
@@ -49,6 +49,12 @@ include::man-common/help-version.adoc[]
 
 The renaming has no safeguards by default or without any one of the options *--no-overwrite*, *--interactive* or *--no-act*. If the user has permission to rewrite file names, the command will perform the action without any questions. For example, the result can be quite drastic when the command is run as root in the _/lib_ directory. Always make a backup before running the command, unless you truly know what you are doing.
 
+== EDGE CASES
+
+If the _expression_ is empty, then by default _replacement_ will be added to the start of the filename. With *--all*, _replacement_ will be inserted in between every two characters of the filename, as well as at the start and end.
+
+Normally, only the final path component of a filename is updated. But if either _expression_ or _replacement_ contains a _/_, the full path is updated. This can cause a file to be moved between folders. Creating folders, and moving files between filesystems, is not supported. With *--symlink*, the update is always applied to the link's full path.
+
 == INTERACTIVE MODE
 
 As most standard utilities rename can be used with a terminal device (tty in short) in canonical mode, where the line is buffered by the tty and you press ENTER to validate the user input. If you put your tty in cbreak mode however, rename requires only a single key press to answer the prompt. To set cbreak mode, run for example: