Editors and Mergetools with drracket

README.md

@@ -39,6 +39,7 @@ alias for `git*`.
 (git* rebase main)
 (git* merge feature)
 (git* cherry-pick abc1234)
+(git* mergetool)
 
 (define branch "develop")
 (git* switch (eval branch))
@@ -54,6 +55,7 @@ behavior:
 - `git-remote` returns remote names; `git-remote -v` / `git-remote --verbose` returns separate `(name url fetch|push)` items.
 - `git-stash list` returns `(stash-name description)` items; other stash subcommands keep Git's normal behavior.
 - `git-restore`, `git-reset`, `git-revert`, `git-rebase`, `git-merge`, and `git-cherry-pick` pass Git's command syntax through unchanged.
+- `git-mergetool` uses Git's mergetool interface and prefers a configured or well-known graphical merge tool.
 - `git-diff` renders HTML by default; `--output=-` selects stdout and
   `--output=string` returns a string.
 - `git-show` renders a commit and its diff as HTML by default. `-l` /
@@ -66,7 +68,7 @@ credentials, SSH keys, pull strategy, and other repository configuration.
 ## Commands
 
 The package currently registers commands including `status`, `add`, `commit`,
-`push`, `pull`, `fetch`, `config`, `branch`, `remote`, `stash`, `restore`, `reset`, `revert`, `rebase`, `merge`, `cherry-pick`, `switch`, `clone`, `tag`, `log`,
+`push`, `pull`, `fetch`, `config`, `branch`, `remote`, `stash`, `restore`, `reset`, `revert`, `rebase`, `merge`, `cherry-pick`, `mergetool`, `switch`, `clone`, `tag`, `log`,
 `rev-list`, `diff`, `show`, `grep`, `help`, `version`, and `new-version`.
 
 Most are also exported as direct procedures such as `git-status`, `git-add`,
@@ -131,3 +133,40 @@ raised. This prevents a bad token from remaining in the credential cache.
 
 A custom handler can still be installed through
 `current-git-authentication-handler`.
+
+
+## GUI editor and merge tool
+
+git-cli looks for a GUI editor and passes it to Git through `GIT_EDITOR` and
+`GIT_SEQUENCE_EDITOR` in the environment of the Git subprocess only. It does
+not change the user's global Git configuration.
+
+The editor can be inspected or configured explicitly:
+
+```racket
+(find-editor)
+(set-editor! "code --wait")
+```
+
+The editor search first checks `PATH` and then well-known platform locations.
+On Windows this includes the normal per-user and Program Files locations for
+VS Code, with Notepad as fallback. On macOS the standard Visual Studio Code
+application bundle and TextEdit are recognized. On Linux common `/usr`,
+`/usr/local`, and Snap locations are checked for VS Code, Kate, Gedit, and Xed.
+
+`git-mergetool` stays on top of Git's own mergetool mechanism. If no tool is
+specified explicitly, git-cli prefers a configured or well-known graphical
+tool such as WinMerge, Meld, KDiff3, VS Code, TortoiseMerge, or opendiff.
+The finder checks `PATH` first and then common platform installation locations.
+When a merge tool is found outside `PATH`, git-cli adds that executable's
+directory to the environment of the Git subprocess, so Git's own mergetool
+integration can still find it. If no tool is found, Git is left to select its
+own default.
+
+```racket
+(find-mergetool)
+(find-mergetool-path)
+(set-mergetool! "winmerge")
+(git* mergetool)
+(git* mergetool --tool=meld)
+```