Added git show functionality

scribblings/git.scrbl

@@ -20,7 +20,7 @@ Runs a registered Git @racket[command]. The arguments are passed to the command.
 Registered command symbols are @racket['status], @racket['add],
 @racket['commit], @racket['push], @racket['pull], @racket['branch],
 @racket['clone], @racket['log], @racket['rev-list], @racket['diff],
-@racket['grep], @racket['help], @racket['version], and
+@racket['show], @racket['grep], @racket['help], @racket['version], and
 @racket['new-version].
 
 Most registered commands invoke the Git command with the same name. Some
@@ -94,6 +94,48 @@ extra output lines can also influence how useful @tt{--list} is as a structured
 result.
 }
 
+
+
+@defproc[(git-show [argument any/c] ...) (or/c boolean? string? list?)]{
+Shows a Git object.
+
+For a commit that includes a patch, the default git-cli output is HTML. The
+commit information is shown above the diff and the diff is rendered using the
+same Diff2Html presentation as @racket[git-diff].
+
+The git-cli-specific output options are @tt{--output=html},
+@tt{--output=-}, and @tt{--output=string}. @tt{--output=html} explicitly
+selects the HTML presentation, @tt{--output=-} keeps Git's normal textual
+output, and @tt{--output=string} returns that textual output as a string.
+Options such as @tt{--stat}, @tt{--name-only}, @tt{--name-status}, and
+@tt{--no-patch} default to textual output because they do not normally contain
+a patch.
+
+The git-cli-specific option @tt{--list}, or its short form @tt{-l}, returns a
+Racket value. Without another show-format option it implies @tt{--stat}.
+
+@racketblock[
+(git-show '-l "9741b1c")
+]
+
+The result of @tt{--stat --list} contains @racket['file] and
+@racket['total] items:
+
+@racketblock[
+'((file "README.md" 67 "+++---")
+  (file "main.rkt" 532 "++++-------------------------------------------")
+  (total 9 124 823))
+]
+
+With @tt{--name-only --list}, the result is a list of file names. With
+@tt{--name-status --list}, every result item is the tab-separated Git
+name-status record converted to a list of strings.
+
+@tt{--list}/@tt{-l} cannot be combined with @tt{--output=...}. Only one of
+@tt{--stat}, @tt{--name-only}, and @tt{--name-status} can be used with
+@tt{--list}.
+}
+
 @defproc[(git-grep [argument any/c] ...) list?]{
 Searches tracked files. Each result contains the file, optional line number,
 optional match count, and matched text. Exit status one means that no matches