This enables clients to move back and forth between parsed objects and
text patches. The generated patches are semantically equal to the parsed
object and should re-parse to the same object, but may not be
byte-for-byte identical to the original input.
In my testing, formatted text patches are usually identical to the
input, but there may be cases where this is not true. Binary patches
always differ. This is because Go's 'compress/flate' package ends
streams with an empty block instead of adding the end-of-stream flag to
the last non-empty block, like Git's C implementation. Since the streams
will always be different for this reason, I chose to also enable default
compression (the test patches I generated with Git used no compression.)
The main tests for this feature involve parsing, formatting, and then
re-parsing a patch to make sure we get equal objects.
Formatting is handled by a new internal formatter type, which allows
writing all data to the same stream. This isn't exposed publicly right
now, but will be useful if there's a need for more flexible formatting
functions in the future, like formatting to a user-provided io.Writer.
While empty patches with only a header were parsable, the parser
discarded the preamble content. This meant callers had to handle this
case specially. Now, if we reach the end of the input without finding a
file, Parse() returns the full content of the patch as the preamble.
The previous version of the golangci-lint action would install its own
version of Go, which eventually conflicted with the old pinned version
of the linter I was using. Upgrade the action to avoid this, but also
update Go and the linter while I'm here.
When applying a text fragment that deletes all content in the file, make
sure there is no content left in the source after using all the lines in
the fragment. If there is is extra content, it's a conflict: something
added more lines to the file after generating the patch.
These cover some of the possible errors with delta fragments. Many of
the same tests could be implemented slightly easier by testing the
helper functions, but the infrastructure is already set up to test the
full function.
This is made easier by the bin.go CLI, which can parse and encode binary
patch data. Once parsed, fragments were manipulated with truncate and
dd, encoded, and placed in the patch files.
Covers basic literal and delta application. Input files were created by
using dd and the 'conv=notrunc' option to modify sections of files
created from /dev/urandom. All file start with two null bytes to
convince Git they are binary.
This allows callers to provide patches with commit or email headers and
then retrieve that leading content for additional parsing without
having to identify where the first file in the patch starts.
For now, this uses JSON to print objects on error, which is hard to
debug. It should probably use something like google/go-cmp instead,
because these objects are now too large for direct comparison.
Billy Keyes