Here are a few new features I’ve added to GNU ELPA and upstream GNU Emacs recently. Text is adapted from the in-tree documentation I wrote for the new features. Thanks to everyone who offered feedback on my patches.

New feature to easily bypass Eshell’s own pipelining

Prefixing |, < or > with an asterisk, i.e. *|, *< or *>, will cause the whole command to be passed to the operating system shell. This is particularly useful to bypass Eshell’s own pipelining support for pipelines which will move a lot of data.

This has long been an obstacle when it comes to using Eshell as one’s main shell. The new syntax is easy to use and covers a lot of different use cases.

New Eshell module to help supplying absolute file names to remote commands

After enabling the new eshell-elecslash module, typing a forward slash as the first character of a command line argument will automatically insert the Tramp prefix. The automatic insertion applies only when default-directory is remote and the command is a Lisp function. This frees you from having to keep track of whether commands are Lisp function or external when supplying absolute file name arguments.

This is another attempt to solve an Eshell papercut. Suppose you execute

 cd /
 find /etc -name "*gnu*"

and in reviewing the output of the command, you identify a file /etc/gnugnu that should be moved somewhere else. So you type

mv /etc/gnugnu /tmp

But since mv refers to the local Lisp function eshell/mv, not a remote shell command (unlike find(1)), to say this is to request that the local file /etc/gnugnu be moved into the local /tmp directory. After you enable eshell-elecslash, to then when you type the above mv invocation you will get the following input, which is what you intended:

mv / /

imenu is now bound to M-g i globally

This is a useful command but everyone has to come up with their own binding for it. No longer.

New macro-writing macros, cl-with-gensyms and cl-once-only

These two macros are quite interesting. In the history of Common Lisp-style macros, these are the only two macro-writing macros that have emerged as essential tools for intermediate and advanced macrology. Most any other macro-writing macros are either project- or programmer-specific. In his book on Lisp macros Doug Hoyte proposes an alternative to defmacro, defmacro!, which is just the same as defmacro except that it builds in facilities equivalent to cl-with-gensyms and cl-once-only. I’ve long wanted to have these macros available in core Emacs Lisp, too, and now they are.

New package on GNU ELPA: transient-cycles

Many commands can be conceptualised as selecting an item from an ordered list or ring. Sometimes after running such a command, you find that the item selected is not the one you would have preferred, but the preferred item is nearby in the list. If the command has been augmented with transient cycling, then it finishes by setting a transient map with keys to move backwards and forwards in the list of items, so you can select a nearby item instead of the one the command selected. From the point of view of commands subsequent to the deactivation of the transient map, it is as though the first command actually selected the nearby item, not the one it really selected.

Protesilaos Stavrou helped me test the package and has written up some usage notes.

This is an idea I came up with in 2020, and refined in my init.el since then. This year I made it into a package.