When coding, I often need to search for the references of a variable or a function across multiple files. Usually I enter command mode of vim and do a grep command, memorize the search results and open the files having hits. This common pattern could be dramatically accelerated by a user-defined vim command:
:command Gitgrep :lex system("git grep -n " . shellescape(getreg('/'))).

TL;DR The variable MAKEOVERRIDES passes the variables defined in the make command line to sub-makes (even those make invoked indirectly). Emptying MAKEOVERRIDES can prevent sub-makes from picking up variables unexpected.

GCC has its version written in the .comment section of the executable binaries as shown by commands:

objdump -s --section .comment /path/to/binary
# or pretty print
readelf -p .comment /path/to/binary

4b825dc642cb6eb9a060e54bf8d69288fbee4904 is the hash code to index the “empty tree” (before your first commit) in git version control system.

This post talks about how to get patch work with git.

After switched to use Linux, I use vim-latex to extand vim for LaTeX editing. However, sometimes I would encounter errors like package not found. I thought that is because vim-latex supports limited packages (under ~/.vim/ftplugin/latex-suite/packages/), but actually vim-latex is just the plugin to turn vim into a LaTeX editor, while the complier behind it is something else, for example TeX Live.
TeX Live has its own package manager called tlmgr. This post documents some issues I had to install absent package for TeX Live.

Tips about some special variables used in makefile: automatic variables, $@, $<, $^; wildcard placeholder % in targets and dependencies and $* in recipe; and .DEFAULT_GOAL.