fix(pager): render conflicted Git diffs

[0xferrous]

Summary

When Git is paused during a conflicted merge or rebase, git diff emits a combined diff using diff --cc/diff --combined headers and @@@ hunk syntax. With core.pager = "hunk pager", Hunk previously treated this input as an empty review:

No files match the current filter.

The pager/difftool configuration was valid; Hunk’s patch sanitizer did not support Git’s combined conflict format.

Fix

Normalize combined Git patches into the existing unified patch format before parsing:

• Convert combined file and hunk headers to standard diff --git/@@ syntax.
• Project the result against the first parent.
• Omit lines deleted only from other parents.
• Preserve conflict markers and partially resolved changes.
• Handle binary combined conflicts with no unified hunk.
• Handle --combined-all-paths by retaining the first parent’s path.
• Leave ordinary unified patches unchanged.

This keeps the behavior in the shared patch-sanitization layer used by Hunk’s existing consumers.

Reproduction

1. Configure Hunk as Git’s pager:

   git config --global core.pager "hunk pager"

2. Start a conflicting merge or rebase.

3. Run:

   git diff

Before this change, Hunk displayed an empty review. After this change, it displays the conflicted file and its conflict markers.

Validation

• Focused parser and static pager tests: 42 passed
• bun run typecheck
• oxfmt --check
• git diff --check
• Pre-commit formatting and lint hooks passed
• Manual real-PTY reproduction at 120×34 terminal dimensions
• Added a patch Changeset for hunkdiff

Visual evidence was captured from the real Hunk TUI for the blank before state and rendered after state.

before:

after:

[vercel]

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