Function resolve_diff_request 

pub fn resolve_diff_request(
    repo: &Repository,
    cwd_prefix: Option<&str>,
    request: &DiffRequest,
) -> Result<DiffArguments, ResolveDiffArgumentsError>

Decide what grit diff compares and which paths it is limited to.

Operands before -- that are not revisions but name known paths (in the index, HEAD, or the working tree) are treated as paths, so grit diff file.txt and grit diff HEAD~1 file.txt work without --. One operand selects a commit’s own patch, or a tree diff for A..B / A...B (merge base of A and B against B); two operands compare two commits. With no operands the working tree is compared with HEAD, or with DiffRequest::against.

Working-tree pathspecs must match a known path; commit and range pathspecs only need to parse, so paths deleted on either side can still be named. An unresolved operand falls back to a working-tree path only when no path operands or pathspec-file entries were supplied; otherwise its revision error is preserved.

Parameters

• repo - repository the revisions and paths belong to.
• cwd_prefix - path from the work tree root to the process cwd (from pathdiff); None at the root, when unknown, or in a bare repository.
• request - flags and operands as given.

Errors

• Flag conflicts: ResolveDiffArgumentsError::StagedAndUnstaged, StagedWithRevisions, UnstagedWithRevisions, TooManyRevisions, AgainstWithCommits, RangeWithSecondRevision.
• Revisions: UnresolvedRevision, NotACommit, NoMergeBase, MultipleMergeBases.
• Working tree: NoWorkTree when the target reads the working tree in a bare repository.
• Paths: Pathspec, or Library wrapping Error::PathspecNoMatch.