std/diff

Differences between texts, and what is done with them.

import "std/diff"

print(unified_diff(read_text("old.txt"), read_text("new.txt"), "old.txt", "new.txt"))
str patched = patch_text(read_text("old.txt"), read_text("fix.patch"))?
MergeResult m = merge3(base, ours, theirs)
print(m.conflicts)

A difference is a list of DiffChanges, in order: a_count items of the first sequence from a_start became b_count items of the second from b_start; what is between changes is the same in both.

Function	Result
`diff_items(a, b, algorithm)`	the changes between two `str[]`: by `"myers"` (the default: the fewest items deleted and inserted, in linear space), `"patience"`, or `"histogram"`, which keep moved and repeated lines apart better
`diff_lines(a, b, algorithm)`	between the lines of two texts
`diff_words(a, b)`, `diff_chars(a, b)`	between their words, spaces, and punctuation, or their characters as people see them
`lines_with_ends(text)`	the lines, each with its line end
`unified_diff(a, b, a_name, b_name, context, algorithm)`	the unified diff of two texts, with `context` lines (3) around each change; `""` when they are the same
`parse_patch(text)`	the `FilePatch`es of a unified diff, as `diff -u` and `git diff` write it: each with `old_name`, `new_name`, and `hunks`
`apply_patch(text, patch)`	the text with a `FilePatch` applied; a hunk not where it says is looked for nearby, and one found nowhere is an `ERROR` of kind `"patch_failed"`
`patch_text(text, patch)`	the same, from the text of a diff of one file
`merge3(base, ours, theirs, ...)`	a `MergeResult`, with the merged `text` and the number of `conflicts`
`inline_changes(old_line, new_line)`	the `removed` and `added` byte `Span`s (`start`, `stop`) of the words that changed, to highlight

merge3 takes a change only one side made, and the same change made on both; changes of both sides to the same or adjacent lines are a conflict, between <<<<<<< ours, =======, and >>>>>>> theirs. Its named arguments ours_label, theirs_label, and base_label name them, and show_base: true adds the base's lines after ||||||| base, as git merge-file --diff3 does.