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merge: add an option to select how incomplete hunks are rendered #88

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Merged
bmwill merged 1 commit into from
Aug 31, 2026
Merged

merge: add an option to select how incomplete hunks are rendered #88

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1 change: 1 addition & 0 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -330,6 +330,7 @@ pub use diff::DiffOptions;
pub use diff::create_patch;
pub use diff::create_patch_bytes;
pub use merge::ConflictStyle;
pub use merge::IncompleteHunkStyle;
pub use merge::MergeOptions;
pub use merge::merge;
pub use merge::merge_bytes;
Expand Down
118 changes: 108 additions & 10 deletions src/merge/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,40 @@ pub enum ConflictStyle {
Diff3,
}

/// Style used when rendering conflict markers after a hunk that ends in an
/// incomplete line (one without a trailing newline).
///
/// An incomplete line can only appear as the final line of a file, so this
/// only affects conflicts that include the end of the file.
#[derive(Copy, Clone, Debug)]
pub enum IncompleteHunkStyle {
/// Appends conflict markers directly to the incomplete line, matching the
/// behavior of GNU `diff3 -m`.
///
/// ```console
/// <<<<<<< ours
/// ours line||||||| original
/// original line=======
/// theirs line>>>>>>> theirs
/// ```
Diff3,

/// Inserts a newline after the incomplete line so that every conflict
/// marker starts at the beginning of a line, matching the behavior of
/// `git merge-file`.
///
/// ```console
/// <<<<<<< ours
/// ours line
/// ||||||| original
/// original line
/// =======
/// theirs line
/// >>>>>>> theirs
/// ```
Git,
}

/// A collection of options for modifying the way a merge is performed
///
/// # Examples
Expand Down Expand Up @@ -145,6 +179,7 @@ pub enum ConflictStyle {
pub struct MergeOptions {
conflict_marker_length: usize,
style: ConflictStyle,
incomplete_hunk_style: IncompleteHunkStyle,
}

impl MergeOptions {
Expand All @@ -153,10 +188,12 @@ impl MergeOptions {
/// ## Defaults
/// * conflict_marker_length = 7
/// * style = ConflictStyle::Diff3
/// * incomplete_hunk_style = IncompleteHunkStyle::Diff3
pub fn new() -> Self {
Self {
conflict_marker_length: DEFAULT_CONFLICT_MARKER_LENGTH,
style: ConflictStyle::Diff3,
incomplete_hunk_style: IncompleteHunkStyle::Diff3,
}
}

Expand All @@ -172,6 +209,13 @@ impl MergeOptions {
self
}

/// Set the style used when rendering conflict markers after a hunk that
/// ends in an incomplete line
pub fn set_incomplete_hunk_style(&mut self, style: IncompleteHunkStyle) -> &mut Self {
self.incomplete_hunk_style = style;
self
}

/// Merge two files, given a common ancestor, based on the configured options
pub fn merge<'a>(
&self,
Expand Down Expand Up @@ -200,6 +244,7 @@ impl MergeOptions {
&merge,
self.conflict_marker_length,
self.style,
self.incomplete_hunk_style,
)
}

Expand Down Expand Up @@ -231,6 +276,7 @@ impl MergeOptions {
&merge,
self.conflict_marker_length,
self.style,
self.incomplete_hunk_style,
)
}
}
Expand Down Expand Up @@ -556,6 +602,7 @@ fn output_result<'a, T: ?Sized>(
merge: &[MergeRange<T>],
marker_len: usize,
style: ConflictStyle,
incomplete_hunk_style: IncompleteHunkStyle,
) -> Result<String, String> {
let mut conflicts = 0;
let mut output = String::new();
Expand All @@ -566,17 +613,35 @@ fn output_result<'a, T: ?Sized>(
output.extend(ancestor[range.range()].iter().copied());
}
MergeRange::Conflict(ancestor_range, ours_range, theirs_range) => {
add_conflict_marker(&mut output, '<', marker_len, Some("ours"));
add_conflict_marker(
&mut output,
'<',
marker_len,
Some("ours"),
incomplete_hunk_style,
);
output.extend(ours[ours_range.range()].iter().copied());

if let ConflictStyle::Diff3 = style {
add_conflict_marker(&mut output, '|', marker_len, Some("original"));
add_conflict_marker(
&mut output,
'|',
marker_len,
Some("original"),
incomplete_hunk_style,
);
output.extend(ancestor[ancestor_range.range()].iter().copied());
}

add_conflict_marker(&mut output, '=', marker_len, None);
add_conflict_marker(&mut output, '=', marker_len, None, incomplete_hunk_style);
output.extend(theirs[theirs_range.range()].iter().copied());
add_conflict_marker(&mut output, '>', marker_len, Some("theirs"));
add_conflict_marker(
&mut output,
'>',
marker_len,
Some("theirs"),
incomplete_hunk_style,
);
conflicts += 1;
}
MergeRange::Ours(range) => {
Expand All @@ -603,8 +668,12 @@ fn add_conflict_marker(
marker: char,
marker_len: usize,
filename: Option<&str>,
incomplete_hunk_style: IncompleteHunkStyle,
) {
if !output.is_empty() && !output.ends_with('\n') {
if matches!(incomplete_hunk_style, IncompleteHunkStyle::Git)
&& !output.is_empty()
&& !output.ends_with('\n')
{
output.push('\n');
}
for _ in 0..marker_len {
Expand All @@ -625,6 +694,7 @@ fn output_result_bytes<'a, T: ?Sized>(
merge: &[MergeRange<T>],
marker_len: usize,
style: ConflictStyle,
incomplete_hunk_style: IncompleteHunkStyle,
) -> Result<Vec<u8>, Vec<u8>> {
let mut conflicts = 0;
let mut output: Vec<u8> = Vec::new();
Expand All @@ -637,23 +707,47 @@ fn output_result_bytes<'a, T: ?Sized>(
.for_each(|line| output.extend_from_slice(line));
}
MergeRange::Conflict(ancestor_range, ours_range, theirs_range) => {
add_conflict_marker_bytes(&mut output, b'<', marker_len, Some(b"ours"));
add_conflict_marker_bytes(
&mut output,
b'<',
marker_len,
Some(b"ours"),
incomplete_hunk_style,
);
ours[ours_range.range()]
.iter()
.for_each(|line| output.extend_from_slice(line));

if let ConflictStyle::Diff3 = style {
add_conflict_marker_bytes(&mut output, b'|', marker_len, Some(b"original"));
add_conflict_marker_bytes(
&mut output,
b'|',
marker_len,
Some(b"original"),
incomplete_hunk_style,
);
ancestor[ancestor_range.range()]
.iter()
.for_each(|line| output.extend_from_slice(line));
}

add_conflict_marker_bytes(&mut output, b'=', marker_len, None);
add_conflict_marker_bytes(
&mut output,
b'=',
marker_len,
None,
incomplete_hunk_style,
);
theirs[theirs_range.range()]
.iter()
.for_each(|line| output.extend_from_slice(line));
add_conflict_marker_bytes(&mut output, b'>', marker_len, Some(b"theirs"));
add_conflict_marker_bytes(
&mut output,
b'>',
marker_len,
Some(b"theirs"),
incomplete_hunk_style,
);
conflicts += 1;
}
MergeRange::Ours(range) => {
Expand Down Expand Up @@ -686,8 +780,12 @@ fn add_conflict_marker_bytes(
marker: u8,
marker_len: usize,
filename: Option<&[u8]>,
incomplete_hunk_style: IncompleteHunkStyle,
) {
if !output.is_empty() && output.last() != Some(&b'\n') {
if matches!(incomplete_hunk_style, IncompleteHunkStyle::Git)
&& !output.is_empty()
&& output.last() != Some(&b'\n')
{
output.push(b'\n');
}
for _ in 0..marker_len {
Expand Down
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