From 8eedca7656480f64014be4636b7269a25548ffcf Mon Sep 17 00:00:00 2001
From: Ori Bernstein <ori@eigenstate.org>
Date: Sun, 22 May 2022 16:41:47 +0000
Subject: [PATCH] diff: retain original file names

When diffing non-regular files, like /dev/null,
pipes, and similar, diff will generate a temp
file to diff against. This is the right thing
to do, but the temp file leaks into the diff.

This patch retains the original file name all
the way through to diff output.
---
 sys/src/cmd/diff/diff.h    | 4 ++--
 sys/src/cmd/diff/diffio.c  | 9 ++++-----
 sys/src/cmd/diff/diffreg.c | 6 +++---
 sys/src/cmd/diff/main.c    | 6 +++---
 4 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/sys/src/cmd/diff/diff.h b/sys/src/cmd/diff/diff.h
index 370dccb20..8aca0439f 100644
--- a/sys/src/cmd/diff/diff.h
+++ b/sys/src/cmd/diff/diff.h
@@ -23,8 +23,8 @@ void *emalloc(unsigned);
 void *erealloc(void *, unsigned);
 void diff(char *, char *, int);
 void diffdir(char *, char *, int);
-void diffreg(char *, char *);
-Biobuf *prepare(int, char *);
+void diffreg(char *, char *, char *, char *);
+Biobuf *prepare(int, char *, char *);
 void panic(int, char *, ...);
 void check(Biobuf *, Biobuf *);
 void change(int, int, int, int);
diff --git a/sys/src/cmd/diff/diffio.c b/sys/src/cmd/diff/diffio.c
index b5b4964c1..f9608d8d5 100644
--- a/sys/src/cmd/diff/diffio.c
+++ b/sys/src/cmd/diff/diffio.c
@@ -104,7 +104,7 @@ readhash(Biobuf *bp, char *buf)
 }
 
 Biobuf *
-prepare(int i, char *arg)
+prepare(int i, char *arg, char *orig)
 {
 	Line *p;
 	int j, h;
@@ -143,11 +143,10 @@ prepare(int i, char *arg)
 	file[i] = p;
 	input[i] = bp;			/*fix*/
 	if (i == 0) {			/*fix*/
-		file1 = arg;
+		file1 = orig;
 		firstchange = 0;
-	}
-	else
-		file2 = arg;
+	} else
+		file2 = orig;
 	return bp;
 }
 
diff --git a/sys/src/cmd/diff/diffreg.c b/sys/src/cmd/diff/diffreg.c
index 1b8f4e5be..4d90c40ca 100644
--- a/sys/src/cmd/diff/diffreg.c
+++ b/sys/src/cmd/diff/diffreg.c
@@ -363,16 +363,16 @@ cmp(Biobuf* b1, Biobuf* b2)
 }
 
 void
-diffreg(char *f, char *t)
+diffreg(char *f, char *fo, char *t, char *to)
 {
 	Biobuf *b0, *b1;
 	int k;
 
 	binary = 0;
-	b0 = prepare(0, f);
+	b0 = prepare(0, f, fo);
 	if (!b0)
 		return;
-	b1 = prepare(1, t);
+	b1 = prepare(1, t, to);
 	if (!b1) {
 		Bterm(b0);
 		return;
diff --git a/sys/src/cmd/diff/main.c b/sys/src/cmd/diff/main.c
index d91c85561..385537207 100644
--- a/sys/src/cmd/diff/main.c
+++ b/sys/src/cmd/diff/main.c
@@ -149,7 +149,7 @@ diff(char *f, char *t, int level)
 			Bprint(&stdout, "Common subdirectories: %s and %s\n", fp, tp);
 	}
 	else if (REGULAR_FILE(fsb) && REGULAR_FILE(tsb))
-		diffreg(fp, tp);
+		diffreg(fp, f, tp, t);
 	else {
 		if (REGULAR_FILE(fsb)) {
 			if ((p = utfrrune(f, '/')) == 0)
@@ -157,14 +157,14 @@ diff(char *f, char *t, int level)
 			else
 				p++;
 			if (mkpathname(tb, tp, p) == 0)
-				diffreg(fp, tb);
+				diffreg(fp, f, tb, t);
 		} else {
 			if ((p = utfrrune(t, '/')) == 0)
 				p = t;
 			else
 				p++;
 			if (mkpathname(fb, fp, p) == 0)
-				diffreg(fb, tp);
+				diffreg(fb, f, tp, t);
 		}
 	}
 	free(fsb);