Compare and Merge input encoding

This family ports per-pane encoding reload separately from output format conversion. It covers two-file/historical comparisons and three-way conflict, standalone and patch merge inputs. Complete editor parity and signed/physical acceptance remain open.

Source contract

Pinned TortoiseGit 7338078f8ddd924b8cddee35f512f2286072136d, src/TortoiseMerge/MainFrm.cpp:

AdjustUnicodeTypeForLoad, lines 3526–3554, selects a concrete reader and maps UTF-8/UTF-16 BOM menu variants to their corresponding load encoding.
OnEncodingLeft/Right/Bottom, lines 3557–3626, capture Control: ordinary selection changes output type; Control changes one source's decoder, retains that encoding and calls LoadViews.
OnUpdateEncodingLeft/Right/Bottom, lines 3693–3724, enable input reload even for read-only panes while Control is held. Read-only EOL conversion stays disabled.

Native implementation

The encoding controls retain ordinary output conversion and offer an explicit Reload with encoding submenu. Control-selection of an encoding follows the source reload gesture. Captured pane/role receipts prevent a menu opened for an old document or pane from changing its successor. The explicit submenu provides the same reload action without requiring a modifier, including read-only inputs.

The selected decoder reads the original bytes, independently for each input. It does not re-encode an already decoded string. Two-pane comparison retains physical input identity across left/right switching. Three-way documents retain Base/Mine/Theirs raw inputs, including the actual conflict-stage/rebase mapping, and regenerate through the current merge engine. Ordinary reload reapplies accepted overrides; a new document starts with its own input policy. BOM choices select a reader rather than adding a BOM to source files.

Reload uses existing dirty Save/Discard/Cancel choices. Cancel preserves the draft, history and accepted decoder. A successful reload publishes the decoded document, alignment/merge result, format metadata and navigation together, and starts a fresh editing history. Failed or cancelled decoding retains the current accepted view and overrides. A Save explicitly chosen before reload may already have written the prior draft even if the subsequent decoder fails.

Input reinterpretation itself writes neither source files nor Git's index. Output encoding/EOL conversion remains a separate draft edit requiring Save. Read-only source panes continue to reject EOL edits and output conversion.

Validation and remaining work

The dated grouped checkpoint is merge-input-encoding-2026-10-21.json. The checkpoint passed 63 focused Core methods, the Debug build and eight native case/engine pairs across the recorded compile, selector and fixture repairs. Core includes real reversed rebase stages and unchanged index/working snapshots. Native checks include captured menus, historical/undecoded inputs, source swaps, raw/BOM comparison children, failed decode retention and owned dirty reloads. It records actual checks, failures and focused repairs; it does not imply every encoding, external filter/provider or source state was exercised.

Actual full-window light and dark captures show both reloaded UTF-8 inputs, native encoding controls, source colors and separate read-only EOL state. The window chrome is inactive. These captures were reviewed individually and the capture owner was closed immediately afterward.

Physical Control gestures/popups, keyboard/VoiceOver, every code page and malformed input combination, signed file grants and minimum-version/Intel acceptance remain open. Complete TortoiseMerge layout/behavior, current hosted integration, Finder and App Store distribution have separate gates.