xdiff: drop unused mmfile parameters from xdl_do_histogram_diff()

These are no longer used since 9df0fc3d57 (xdiff: fix a memory leak,
2022-02-16), as the caller is expected to call xdl_prepare_env() itself.
After that change the histogram code only examines the prepared
xdfenv_t, not the original buffers.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

xdiff/xdiffi.c

@@ -326,7 +326,7 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 	}
 
 	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF) {
-		res = xdl_do_histogram_diff(mf1, mf2, xpp, xe);
+		res = xdl_do_histogram_diff(xpp, xe);
 		goto out;
 	}
 

xdiff/xdiffi.h

@@ -58,7 +58,6 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		  xdemitconf_t const *xecfg);
 int xdl_do_patience_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 		xdfenv_t *env);
-int xdl_do_histogram_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
-		xdfenv_t *env);
+int xdl_do_histogram_diff(xpparam_t const *xpp, xdfenv_t *env);
 
 #endif /* #if !defined(XDIFFI_H) */

xdiff/xhistogram.c

@@ -362,8 +362,7 @@ out:
 	return result;
 }
 
-int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
-	xpparam_t const *xpp, xdfenv_t *env)
+int xdl_do_histogram_diff(xpparam_t const *xpp, xdfenv_t *env)
 {
 	return histogram_diff(xpp, env,
 		env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,