libra apply

Check whether a unified-diff patch applies cleanly — an MVP of git apply --check. This version validates only: it parses the patch, safety-checks every target path, and test-applies each file's hunks against the current working tree without writing anything.

Synopsis

libra apply --check [-p<n>] [<patch>...]

Description

apply --check reads one or more unified-diff patches (from the named files, or from stdin when none are given), splits them into per-file sections, and for each file:

1. parses the hunks (a malformed patch is a fatal error);
2. resolves the target path, stripping <n> leading components (-p<n>, default 1) and rejecting any path that is absolute, contains .., contains a NUL, or points inside .libra/;
3. test-applies the hunks to the current file content (an empty base for a new-file patch whose source is /dev/null).

If every file applies, the exit code is 0; if any file does not apply, it is 1. The working tree is never modified. Actually applying a patch (with an atomic temp-file + rename) is a planned future extension; --check is required today.

Patches larger than 64 MiB are rejected.

Options

Option	Description	Example
--check	Validate without writing (required in this version).	libra apply --check fix.patch
-p<n>	Strip <n> leading path components from each path (default 1).	libra apply --check -p0 fix.patch
--json / --machine	Structured output: { applies, files }.	libra --json apply --check fix.patch

Exit codes

Code	Meaning
0	The patch applies cleanly.
1	The patch does not apply (conflicting context or a missing target).
128	Not inside a repository, --check was omitted, the patch is malformed/oversized/non-UTF-8, or a target path is unsafe.

Examples

# Will this patch apply to the current tree?
libra apply --check fix.patch && echo "clean"

# Patch made without a/ b/ prefixes
libra apply --check -p0 fix.patch

# From a pipeline
git format-patch -1 --stdout | libra apply --check

Comparison with Git

Task	Libra	Git
Check a patch	libra apply --check p	git apply --check p
Path strip	libra apply --check -p0 p	git apply --check -p0 p

Differences and deferred features: actually applying the patch (without --check), --index / --cached, --3way, --reverse, --unidiff-zero, binary patches, and rename/mode hunks are not yet supported. Conflict markers are never written — --check only reports.