Arcane programming magics

Software development has a high learning curve, in part due to the lack of discoverability of useful features.

Here are some useful things that I either learned by accident or by somebody else passing on their arcane wisdom to me.

git

.git/config is the text file that all the git configuration commands edit, and you can edit by hand.
git reflog shows you all git references ever visited; very useful for restoring work thought to be lost.
set environment variable GIT_TRACE to see what git is doing when it doesn't do what you'd expect

you can close an unresponsive ssh session with ~.
ssh is really hard to get working as intended; add verbosity with ssh -vv <domain> to potentially get an idea of what the program is doing and what you can do

exit status 0 is success, so conditionals like if <some command that succeeds> use inverted logic from the usual "if true"
you can see the exit status with echo $? in bash / zsh or echo $status in fish
hit control-t to transpose characters around the cursor in shell (and most macos text inputs). Very handy to correct typos
colored text (and a lot of shell features) are based on "printing" escape sequences; for example echo -e '\e[0;33mhi\e[0;37mthere'
in addition to control-c "interrupt" to exit a process, you can control-\ "whack" a process to force kill it
aliases in bash and abbrs in fish will save you a lot of typing

putting the word debugger in your code will pause at that point if you have devtools open

in ipython, type a question mark after an object to see some info about it, and 2 question marks to see its source code. Also works in jupyter
the current directory cannot be imported from by default. EXPORT PYTHONPATH=. to be able to import from the current directory

you can access your router settings at 192.168.0.1 or sometimes 192.168.1.1. If that doesn't work some routers have magic log-in pages that the routers intercept, like router.asus.com

there's this battery on your motherboard that keeps the circuit "on" so that low-level settings can be persisted. If you pop it out and put it back in, it will reset your basic computer settings
if a laptop won't turn on at all, try disconnecting the battery and connecting it to power. This kept my 2014 macbook air working for years

command-shift-4 takes a screenshot; from the reticule interface you can drag for a rectangle or hit space to capture a window.
command-control-shift-4 takes a screenshot and copies it to your clipboard
command-down opens a file from the file browser. I wish return did this but that renames it.
command-up goes up the file hierarchy.
You can change volume by sub-rectangle increments: hold option+shift and hit the brightness keys

adding a space to the start of a line in source editing mode will make it monospaced like a <pre>