Fix the empty result issue in add -p

[norisio]

Related Issues: #328, #557

Details of the issue

Current delta can't handle CRLF-ending diff hunks at least when used through git add -p. The reason here:

• bytelines library (used here) strips CRs (b'\r', 0x0D) as well as LFs (b'\n', 0x0A) when it splits bytes into lines.
  • Find the operations here.
• So there shouldn't be any CRs in lines: ByteLines<BufRead>.
• However, git inserts some ansi control characters between CR and LF:
  
• So bytelines library can't find and leaves the CR in lines.
• CR will be emitted directly into a terminal (at least when delta used through git add -p). Thus the rendered result will be blank (CR erases the line).

What I changed

When ingest_line, delta strips the trailing CR.

Before:

After:

[dandavison]

This (with the explanation) looks great @norisio, thank you! I've set the tests running on Github actions. Would you be able to add a test for the bug you've fixed? There are lots of examples in the codebase to follow, for example one possible style of test is the end-to-end type tests in test_example_diffs.rs, but if you prefer more of a unit test style that would be good too.

[norisio]

OK, will try.

[norisio]

I added a testcase. GIT_DIFF_SINGLE_HUNK_WITH_SEQUENCE_OF_CR_ESCAPE_SEQUENCES_LF contains the "harmful" pattern CR-ansi-LF.

@dandavison Could you check the content?

On master + testcase:

$ cargo test  orphan
    Finished test [unoptimized + debuginfo] target(s) in 0.05s
     Running target/debug/deps/delta-170397dd0efbb98e

running 1 test
test tests::test_example_diffs::tests::test_orphan_carriage_return_is_stripped ... FAILED

failures:
(snip)

On this branch:

$ cargo test  orphan
    Finished test [unoptimized + debuginfo] target(s) in 4.75s
     Running target/debug/deps/delta-170397dd0efbb98e

running 1 test
test tests::test_example_diffs::tests::test_orphan_carriage_return_is_stripped ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 233 filtered out; finished in 1.86s

[dandavison]

Awesome, thank you!

[dandavison]

Thanks very much for this work @norisio.