This directory contains C code (GNU dialect, Linux only) that summarizes and commits the changes from try, in try-summary and try-commit, respectively.

You do not need these utilities to use try, which has POSIX shell fallback implementations.

Every time try starts up, it looks for these executables on its path; if found, it will use them---otherwise it will use the shell fallbacks. The shell fallbacks are not quite as robust as these utilities and may behave strangely on files with newlines in their names.

These are meant to short, simple scripts.

In order to make sure that we keep them parallel, both files are annotated with TRYCASE(changed, local) forms in comments that identify which case is being handled.

Here changed and local adhere to lf the following grammar:

changed ::= f | opaque | whiteout
local ::= f | *
f ::= file | dir | symlink | nonexist

The script ../scripts/check_trycase.sh will check to make sure that all cases are considered (excepting TRYCASE(opaque, nonexist), which should not happen). If new files need to do a case analysis on how changed files and local files relate, annotate each case with // TRYCASE(cf, lf) and add a check_file call to the check_trycase.sh script.

We rely on user.overlay.opaque to be set for opaque directories, which we can assume will happen because try sets -o userxattr when it mounts the overlay.

We do not handle redirect directories, instead relying on cp/mv to do the copying.

We have not seen user.overlay.whiteout in practice---perhaps it only gets made when you can't mknod a (0,0) character device on the upperdir filesystem?