Git Performance Optimization Features

created or read from. UNTRACKED CACHE --------------- This cache is meant to speed up commands that involve determining untracked files such as `git status`. This feature works by recording the mtime of the working tree directories and then omitting reading directories and stat calls against files in those directories whose mtime hasn't changed. For this to work the underlying operating system and file system must change the `st_mtime` field of directories if files in the directory are added, modified or deleted. You can test whether the filesystem supports that with the `--test-untracked-cache` option. The `--untracked-cache` option used to implicitly perform that test in older versions of Git, but that's no longer the case. If you want to enable (or disable) this feature, it is easier to use the `core.untrackedCache` configuration variable (see linkgit:git-config[1]) than using the `--untracked-cache` option to `git update-index` in each repository, especially if you want to do so across all repositories you use, because you can set the configuration variable to `true` (or `false`) in your `$HOME/.gitconfig` just once and have it affect all repositories you touch. When the `core.untrackedCache` configuration variable is changed, the untracked cache is added to or removed from the index the next time a command reads the index; while when `--[no-|force-]untracked-cache` are used, the untracked cache is immediately added to or removed from the index. Before 2.17, the untracked cache had a bug where replacing a directory with a symlink to another directory could cause it to incorrectly show files tracked by git as untracked. See the "status: add a failing test showing a core.untrackedCache bug" commit to git.git. A workaround for that is (and this might work for other undiscovered bugs in the future): ---------------- $ git -c core.untrackedCache=false status ---------------- This bug has also been shown to affect non-symlink cases of replacing a directory with a file when it comes to the internal structures of the untracked cache, but no case has been reported where this resulted in wrong "git status" output. There are also cases where existing indexes written by git versions before 2.17 will reference directories that don't exist anymore, potentially causing many "could not open directory" warnings to be printed on "git status". These are new warnings for existing issues that were previously silently discarded. As with the bug described above the solution is to one-off do a "git status" run with `core.untrackedCache=false` to flush out the leftover bad data. FILE SYSTEM MONITOR ------------------- This feature is intended to speed up git operations for repos that have large working directories. It enables git to work together with a file system monitor (see linkgit:git-fsmonitor{litdd}daemon[1] and the "fsmonitor-watchman" section of linkgit:githooks[5]) that can inform it as to what files have been modified. This

This section discusses Git features aimed at improving performance, including the untracked cache for speeding up commands like git status, and the file system monitor for large working directories, along with configuration options, bug fixes, and workarounds for potential issues.