cmd/fix: remove all functionality

The buildtag fixer has been incorporated into the vet analyzer
of the same name; all other fixers were already no-ops since
CL 695855.

Fixes #73605
Updates #71859

Change-Id: I90b6c730849a5ecbac3e6fb6fc0e062b5de74831
Reviewed-on: https://go-review.googlesource.com/c/go/+/706758
Reviewed-by: Michael Matloob <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: adonovan

src/cmd/fix/buildtag.go

@@ -9,29 +9,12 @@ the necessary changes to your programs.
 
 Usage:
 
-	go tool fix [-r name,...] [path ...]
+	go tool fix [ignored...]
 
-Without an explicit path, fix reads standard input and writes the
-result to standard output.
-
-If the named path is a file, fix rewrites the named files in place.
-If the named path is a directory, fix rewrites all .go files in that
-directory tree.  When fix rewrites a file, it prints a line to standard
-error giving the name of the file and the rewrite applied.
-
-If the -diff flag is set, no files are rewritten. Instead fix prints
-the differences a rewrite would introduce.
-
-The -r flag restricts the set of rewrites considered to those in the
-named list.  By default fix considers all known rewrites.  Fix's
-rewrites are idempotent, so that it is safe to apply fix to updated
-or partially updated code even without using the -r flag.
-
-Fix prints the full list of fixes it can apply in its help output;
-to see them, run go tool fix -help.
-
-Fix does not make backup copies of the files that it edits.
-Instead, use a version control system's “diff” functionality to inspect
-the changes that fix makes before committing them.
+This tool is currently in transition. All its historical fixers were
+long obsolete and have been removed, so it is currently a no-op. In
+due course the tool will integrate with the Go analysis framework
+(golang.org/x/tools/go/analysis) and run a modern suite of fix
+algorithms; see https://go.dev/issue/71859.
 */
 package main