git update-index --assume-unchanged on directory

The find command from GNU Findutils has a -exec option which removes most of the hassle of using xargs, although its syntax is a little special. It does however deal perfectly with filenames with spaces.

This command will get git to assume all files in and under the listed directory are unchanged:

find path/to/dir -type f -exec git update-index --assume-unchanged '{}' \;

Find takes every argument after -exec until ; (which you have to escape lest your shell eats it) and runs it once for each file found, while replacing {} (again, single quoted so your shell won't eat it) with the found file's name.

Using find's matching criteria (maximum recursion depth, whether the match is a file or is a directory, whether the filename matches an expression) and -exec you can do all sort of powerful things.

Not sure about other implementations of the find command. YMMV.

git update-index wants the file names on its command line, not on its standard input.

Step 1:

cd into the folder you want to assume is unchanged

Step 2:

You can do either this:

git update-index --assume-unchanged $(git ls-files | tr '\n' ' ')

or

git ls-files | tr '\n' ' ' | xargs git update-index --assume-unchanged

Although, with either case, file names with spaces will be problematic. If you have those, you can use this:

git ls-files -z | xargs -0 git update-index --assume-unchanged

Edit: incorporated input from @MatthewScharley regarding git ls-files -z.

Windows Commands

Note: If you're on windows, use Git Bash to run these commands

Add the directory name to .git/info/exclude. This works for untracked files.