🐛 panic associated with side-by-side wrapping operations

[dandavison]

delta 0.10 has introduced a regression as reported by @alerque in #794 (comment) : a panic can be triggered by a colorMoved line under side-by-side cc @th1000s .

Using diff-codes.txt

delta --no-gitconfig --side-by-side < diff-codes.txt

Triggering the bug depends on terminal size: in the following output t1 is the syntax_style_sections string concatenation and t2 is the diff_style_sections string concatenation.

[src/wrapping.rs:292] t1 = "As I swore in my wrath, 'They shall not enter my rest.'\"\n"
[src/wrapping.rs:293] t2 = "As I swore in my wrath, 'They shall not enter my rest.'\""
thread 'main' panicked at 'String mismatch encountered while superimposing style sections: '↵' vs '↴'', src/paint.rs:869:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[dandavison]

The bug is related to the fact that, while both line and raw_line start off with no terminating newline character:

[src/handlers/hunk.rs:73] &self.line = "+As I swore in my wrath, 'They shall not enter my rest.'\""
[src/handlers/hunk.rs:74] &self.raw_line = "\u{1b}[1;36m+\u{1b}[m\u{1b}[1;36mAs I swore in my wrath, 'They shall not enter my rest.'\"\u{1b}[m"

Later on, during side-by-side wrapping, a newline has been appended to the "syntax" version of the line (which derives from line) but is missing from the "diff" version of the line (which derived from raw_line):

[src/wrapping.rs:292] t1 = "As I swore in my wrath, 'They shall not enter my rest.'\"\n"
[src/wrapping.rs:293] t2 = "As I swore in my wrath, 'They shall not enter my rest.'\""

This difference is not present at tag 0.9.2.