Shannon Booth
e0ae942bae
"C:\foo" names the root of drive C, but "C:foo" names foo relative to whatever the current directory on C happens to be. Classifying the second as absolute means it is resolved from a root it does not name. Rejecting absolute names was also the only thing keeping a drive-relative name out of a patch, so is_safe_patch_path() now refuses a colon itself. A colon never appears in a Windows file name, since "file:stream" names an alternate data stream of "file" rather than a file of that name.
Patch
Patch is an implementation of the Unix tool patch.
Goals
- Cross-platform
- Compatible with existing patch implementations
- Compatible with POSIX
How to use
Generate a patch
Generate a patch file using a tool such as git or the diff utility:
# Generate a file 'file-orig.txt' with contents:
# > a
# > b
# > c
echo 'a\nb\nc\n' > file-orig.txt
# Generate a file 'file-new.txt' with contents:
# > a
# > c
echo 'a\nc\n' > file-new.txt
# Generate a unified patch to a file named 'diff.patch' showing 'file-orig.txt'
# has the line 'b' removed when compared to 'file-new.txt'.
diff -u file-orig.txt file-new.txt > diff.patch
Supported patch formats are "normal", "context", "unified" and ed scripts
produced by diff -e.
Applying the patch
Run patch using the generated patch file:
patch --input diff.patch
file-orig.txt should have been patched, removing the line b to match the
contents of file-new.txt.
Cross platform behavior
Patch is written to support Windows, Linux, BSD's and other Unix like systems.
Newline handling
A line that has a different line ending to another (CRLF vs LF) will be considered
to not match. The flag --ignore-whitespace can be used so that lines with different
line endings but the same content will be considered equal.
The flag --newline-output can be used to change how newlines will be output
in patched files.
native: will write the entire contents of the file in native line endings (CRLF\r\non Windows, LF\non Unix).lf: will write the file with LF\nline endings.crlf: will write the file with CRLF\r\nline endings.preserve: will attempt to use same line endings as lines in the file being patched.
By default, patch will select the preserve option.
Path handling
Patch will parse and apply patches using the host systems path separation
semantics. For example, \ characters are treated as path separators on
Windows, but as part of the file name on Unix-like systems.
Symlinks
Symlinks in extended-format patches are supported on Unix like systems. Symlinks are not supported on Windows, and result in the patch failing.
Build & test
Patch is built with cmake. It can be built with the following commands:
cmake -S . -B build
cmake --build build
Tests can be enabled with the -DBUILD_TESTING=On, with coverage information
reported with the coverage target if -DPATCH_ENABLE_COVERAGE=On is enabled.