1 files changed, 327 insertions, 215 deletions

diff --git a/diff.c b/diff.c
index 68bb8c5a84..4dfe6609d0 100644
--- a/diff.c
+++ b/diff.c
@@ -2,6 +2,7 @@
  * Copyright (C) 2005 Junio C Hamano
  */
 #include "cache.h"
+#include "tempfile.h"
 #include "quote.h"
 #include "diff.h"
 #include "diffcore.h"
@@ -12,7 +13,7 @@
 #include "run-command.h"
 #include "utf8.h"
 #include "userdiff.h"
-#include "sigchain.h"
+#include "submodule-config.h"
 #include "submodule.h"
 #include "ll-merge.h"
 #include "string-list.h"
@@ -42,7 +43,7 @@ static long diff_algorithm;
 
 static char diff_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_RESET,
-	GIT_COLOR_NORMAL,	/* PLAIN */
+	GIT_COLOR_NORMAL,	/* CONTEXT */
 	GIT_COLOR_BOLD,		/* METAINFO */
 	GIT_COLOR_CYAN,		/* FRAGINFO */
 	GIT_COLOR_RED,		/* OLD */
@@ -52,23 +53,23 @@ static char diff_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_NORMAL,	/* FUNCINFO */
 };
 
-static int parse_diff_color_slot(const char *var, int ofs)
+static int parse_diff_color_slot(const char *var)
 {
-	if (!strcasecmp(var+ofs, "plain"))
-		return DIFF_PLAIN;
-	if (!strcasecmp(var+ofs, "meta"))
+	if (!strcasecmp(var, "context") || !strcasecmp(var, "plain"))
+		return DIFF_CONTEXT;
+	if (!strcasecmp(var, "meta"))
 		return DIFF_METAINFO;
-	if (!strcasecmp(var+ofs, "frag"))
+	if (!strcasecmp(var, "frag"))
 		return DIFF_FRAGINFO;
-	if (!strcasecmp(var+ofs, "old"))
+	if (!strcasecmp(var, "old"))
 		return DIFF_FILE_OLD;
-	if (!strcasecmp(var+ofs, "new"))
+	if (!strcasecmp(var, "new"))
 		return DIFF_FILE_NEW;
-	if (!strcasecmp(var+ofs, "commit"))
+	if (!strcasecmp(var, "commit"))
 		return DIFF_COMMIT;
-	if (!strcasecmp(var+ofs, "whitespace"))
+	if (!strcasecmp(var, "whitespace"))
 		return DIFF_WHITESPACE;
-	if (!strcasecmp(var+ofs, "func"))
+	if (!strcasecmp(var, "func"))
 		return DIFF_FUNCINFO;
 	return -1;
 }
@@ -167,6 +168,11 @@ long parse_algorithm_value(const char *value)
  * never be affected by the setting of diff.renames
  * the user happens to have in the configuration file.
  */
+void init_diff_ui_defaults(void)
+{
+	diff_detect_rename_default = 1;
+}
+
 int git_diff_ui_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
@@ -231,6 +237,8 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 
 int git_diff_basic_config(const char *var, const char *value, void *cb)
 {
+	const char *name;
+
 	if (!strcmp(var, "diff.renamelimit")) {
 		diff_rename_limit_default = git_config_int(var, value);
 		return 0;
@@ -239,14 +247,14 @@ int git_diff_basic_config(const char *var, const char *value, void *cb)
 	if (userdiff_config(var, value) < 0)
 		return -1;
 
-	if (starts_with(var, "diff.color.") || starts_with(var, "color.diff.")) {
-		int slot = parse_diff_color_slot(var, 11);
+	if (skip_prefix(var, "diff.color.", &name) ||
+	    skip_prefix(var, "color.diff.", &name)) {
+		int slot = parse_diff_color_slot(name);
 		if (slot < 0)
 			return 0;
 		if (!value)
 			return config_error_nonbool(var);
-		color_parse(value, var, diff_colors[slot]);
-		return 0;
+		return color_parse(value, diff_colors[slot]);
 	}
 
 	/* like GNU diff's --suppress-blank-empty option  */
@@ -306,11 +314,26 @@ static const char *external_diff(void)
 	return external_diff_cmd;
 }
 
+/*
+ * Keep track of files used for diffing. Sometimes such an entry
+ * refers to a temporary file, sometimes to an existing file, and
+ * sometimes to "/dev/null".
+ */
 static struct diff_tempfile {
-	const char *name; /* filename external diff should read from */
-	char hex[41];
+	/*
+	 * filename external diff should read from, or NULL if this
+	 * entry is currently not in use:
+	 */
+	const char *name;
+
+	char hex[GIT_SHA1_HEXSZ + 1];
 	char mode[10];
-	char tmp_path[PATH_MAX];
+
+	/*
+	 * If this diff_tempfile instance refers to a temporary file,
+	 * this tempfile object is used to manage its lifetime.
+	 */
+	struct tempfile tempfile;
 } diff_temp[2];
 
 typedef unsigned long (*sane_truncate_fn)(char *line, unsigned long len);
@@ -373,7 +396,7 @@ static unsigned long diff_filespec_size(struct diff_filespec *one)
 {
 	if (!DIFF_FILE_VALID(one))
 		return 0;
-	diff_populate_filespec(one, 1);
+	diff_populate_filespec(one, CHECK_SIZE_ONLY);
 	return one->size;
 }
 
@@ -476,30 +499,63 @@ static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line
 	return ws_blank_line(line, len, ecbdata->ws_rule);
 }
 
-static void emit_add_line(const char *reset,
-			  struct emit_callback *ecbdata,
-			  const char *line, int len)
+static void emit_line_checked(const char *reset,
+			      struct emit_callback *ecbdata,
+			      const char *line, int len,
+			      enum color_diff color,
+			      unsigned ws_error_highlight,
+			      char sign)
 {
-	const char *ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
-	const char *set = diff_get_color(ecbdata->color_diff, DIFF_FILE_NEW);
+	const char *set = diff_get_color(ecbdata->color_diff, color);
+	const char *ws = NULL;
 
-	if (!*ws)
-		emit_line_0(ecbdata->opt, set, reset, '+', line, len);
-	else if (new_blank_line_at_eof(ecbdata, line, len))
+	if (ecbdata->opt->ws_error_highlight & ws_error_highlight) {
+		ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
+		if (!*ws)
+			ws = NULL;
+	}
+
+	if (!ws)
+		emit_line_0(ecbdata->opt, set, reset, sign, line, len);
+	else if (sign == '+' && new_blank_line_at_eof(ecbdata, line, len))
 		/* Blank line at EOF - paint '+' as well */
-		emit_line_0(ecbdata->opt, ws, reset, '+', line, len);
+		emit_line_0(ecbdata->opt, ws, reset, sign, line, len);
 	else {
 		/* Emit just the prefix, then the rest. */
-		emit_line_0(ecbdata->opt, set, reset, '+', "", 0);
+		emit_line_0(ecbdata->opt, set, reset, sign, "", 0);
 		ws_check_emit(line, len, ecbdata->ws_rule,
 			      ecbdata->opt->file, set, reset, ws);
 	}
 }
 
+static void emit_add_line(const char *reset,
+			  struct emit_callback *ecbdata,
+			  const char *line, int len)
+{
+	emit_line_checked(reset, ecbdata, line, len,
+			  DIFF_FILE_NEW, WSEH_NEW, '+');
+}
+
+static void emit_del_line(const char *reset,
+			  struct emit_callback *ecbdata,
+			  const char *line, int len)
+{
+	emit_line_checked(reset, ecbdata, line, len,
+			  DIFF_FILE_OLD, WSEH_OLD, '-');
+}
+
+static void emit_context_line(const char *reset,
+			      struct emit_callback *ecbdata,
+			      const char *line, int len)
+{
+	emit_line_checked(reset, ecbdata, line, len,
+			  DIFF_CONTEXT, WSEH_CONTEXT, ' ');
+}
+
 static void emit_hunk_header(struct emit_callback *ecbdata,
 			     const char *line, int len)
 {
-	const char *plain = diff_get_color(ecbdata->color_diff, DIFF_PLAIN);
+	const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
 	const char *frag = diff_get_color(ecbdata->color_diff, DIFF_FRAGINFO);
 	const char *func = diff_get_color(ecbdata->color_diff, DIFF_FUNCINFO);
 	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
@@ -516,15 +572,15 @@ static void emit_hunk_header(struct emit_callback *ecbdata,
 	if (len < 10 ||
 	    memcmp(line, atat, 2) ||
 	    !(ep = memmem(line + 2, len - 2, atat, 2))) {
-		emit_line(ecbdata->opt, plain, reset, line, len);
+		emit_line(ecbdata->opt, context, reset, line, len);
 		return;
 	}
 	ep += 2; /* skip over @@ */
 
 	/* The hunk header in fraginfo color */
-	strbuf_add(&msgbuf, frag, strlen(frag));
+	strbuf_addstr(&msgbuf, frag);
 	strbuf_add(&msgbuf, line, ep - line);
-	strbuf_add(&msgbuf, reset, strlen(reset));
+	strbuf_addstr(&msgbuf, reset);
 
 	/*
 	 * trailing "\r\n"
@@ -538,15 +594,15 @@ static void emit_hunk_header(struct emit_callback *ecbdata,
 		if (*ep != ' ' && *ep != '\t')
 			break;
 	if (ep != cp) {
-		strbuf_add(&msgbuf, plain, strlen(plain));
+		strbuf_addstr(&msgbuf, context);
 		strbuf_add(&msgbuf, cp, ep - cp);
-		strbuf_add(&msgbuf, reset, strlen(reset));
+		strbuf_addstr(&msgbuf, reset);
 	}
 
 	if (ep < line + len) {
-		strbuf_add(&msgbuf, func, strlen(func));
+		strbuf_addstr(&msgbuf, func);
 		strbuf_add(&msgbuf, ep, line + len - ep);
-		strbuf_add(&msgbuf, reset, strlen(reset));
+		strbuf_addstr(&msgbuf, reset);
 	}
 
 	strbuf_add(&msgbuf, line + len, org_len - len);
@@ -562,25 +618,16 @@ static struct diff_tempfile *claim_diff_tempfile(void) {
 	die("BUG: diff is failing to clean up its tempfiles");
 }
 
-static int remove_tempfile_installed;
-
 static void remove_tempfile(void)
 {
 	int i;
 	for (i = 0; i < ARRAY_SIZE(diff_temp); i++) {
-		if (diff_temp[i].name == diff_temp[i].tmp_path)
-			unlink_or_warn(diff_temp[i].name);
+		if (is_tempfile_active(&diff_temp[i].tempfile))
+			delete_tempfile(&diff_temp[i].tempfile);
 		diff_temp[i].name = NULL;
 	}
 }
 
-static void remove_tempfile_on_signal(int signo)
-{
-	remove_tempfile();
-	sigchain_pop(signo);
-	raise(signo);
-}
-
 static void print_line_count(FILE *file, int count)
 {
 	switch (count) {
@@ -601,7 +648,6 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 {
 	const char *endp = NULL;
 	static const char *nneof = " No newline at end of file\n";
-	const char *old = diff_get_color(ecb->color_diff, DIFF_FILE_OLD);
 	const char *reset = diff_get_color(ecb->color_diff, DIFF_RESET);
 
 	while (0 < size) {
@@ -611,8 +657,7 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 		len = endp ? (endp - data + 1) : size;
 		if (prefix != '+') {
 			ecb->lno_in_preimage++;
-			emit_line_0(ecb->opt, old, reset, '-',
-				    data, len);
+			emit_del_line(reset, ecb, data, len);
 		} else {
 			ecb->lno_in_postimage++;
 			emit_add_line(reset, ecb, data, len);
@@ -621,10 +666,10 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 		data += len;
 	}
 	if (!endp) {
-		const char *plain = diff_get_color(ecb->color_diff,
-						   DIFF_PLAIN);
+		const char *context = diff_get_color(ecb->color_diff,
+						     DIFF_CONTEXT);
 		putc('\n', ecb->opt->file);
-		emit_line_0(ecb->opt, plain, reset, '\\',
+		emit_line_0(ecb->opt, context, reset, '\\',
 			    nneof, strlen(nneof));
 	}
 }
@@ -1000,8 +1045,9 @@ static void diff_words_show(struct diff_words_data *diff_words)
 	xpp.flags = 0;
 	/* as only the hunk header will be parsed, we need a 0-context */
 	xecfg.ctxlen = 0;
-	xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, diff_words,
-		      &xpp, &xecfg);
+	if (xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, diff_words,
+			  &xpp, &xecfg))
+		die("unable to generate word diff");
 	free(minus.ptr);
 	free(plus.ptr);
 	if (diff_words->current_plus != diff_words->plus.text.ptr +
@@ -1084,7 +1130,7 @@ static void init_diff_words_data(struct emit_callback *ecbdata,
 		struct diff_words_style *st = ecbdata->diff_words->style;
 		st->old.color = diff_get_color_opt(o, DIFF_FILE_OLD);
 		st->new.color = diff_get_color_opt(o, DIFF_FILE_NEW);
-		st->ctx.color = diff_get_color_opt(o, DIFF_PLAIN);
+		st->ctx.color = diff_get_color_opt(o, DIFF_CONTEXT);
 	}
 }
 
@@ -1160,7 +1206,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 {
 	struct emit_callback *ecbdata = priv;
 	const char *meta = diff_get_color(ecbdata->color_diff, DIFF_METAINFO);
-	const char *plain = diff_get_color(ecbdata->color_diff, DIFF_PLAIN);
+	const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
 	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
 	struct diff_options *o = ecbdata->opt;
 	const char *line_prefix = diff_line_prefix(o);
@@ -1231,7 +1277,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 		}
 		diff_words_flush(ecbdata);
 		if (ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN) {
-			emit_line(ecbdata->opt, plain, reset, line, len);
+			emit_line(ecbdata->opt, context, reset, line, len);
 			fputs("~\n", ecbdata->opt->file);
 		} else {
 			/*
@@ -1243,22 +1289,32 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 			      line++;
 			      len--;
 			}
-			emit_line(ecbdata->opt, plain, reset, line, len);
+			emit_line(ecbdata->opt, context, reset, line, len);
 		}
 		return;
 	}
 
-	if (line[0] != '+') {
-		const char *color =
-			diff_get_color(ecbdata->color_diff,
-				       line[0] == '-' ? DIFF_FILE_OLD : DIFF_PLAIN);
-		ecbdata->lno_in_preimage++;
-		if (line[0] == ' ')
-			ecbdata->lno_in_postimage++;
-		emit_line(ecbdata->opt, color, reset, line, len);
-	} else {
+	switch (line[0]) {
+	case '+':
 		ecbdata->lno_in_postimage++;
 		emit_add_line(reset, ecbdata, line + 1, len - 1);
+		break;
+	case '-':
+		ecbdata->lno_in_preimage++;
+		emit_del_line(reset, ecbdata, line + 1, len - 1);
+		break;
+	case ' ':
+		ecbdata->lno_in_postimage++;
+		ecbdata->lno_in_preimage++;
+		emit_context_line(reset, ecbdata, line + 1, len - 1);
+		break;
+	default:
+		/* incomplete line at the end */
+		ecbdata->lno_in_preimage++;
+		emit_line(ecbdata->opt,
+			  diff_get_color(ecbdata->color_diff, DIFF_CONTEXT),
+			  reset, line, len);
+		break;
 	}
 }
 
@@ -1361,7 +1417,7 @@ static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
 					  const char *name_b)
 {
 	struct diffstat_file *x;
-	x = xcalloc(sizeof (*x), 1);
+	x = xcalloc(1, sizeof(*x));
 	ALLOC_GROW(diffstat->files, diffstat->nr + 1, diffstat->alloc);
 	diffstat->files[diffstat->nr++] = x;
 	if (name_b) {
@@ -1907,11 +1963,11 @@ static void show_dirstat(struct diff_options *options)
 			diff_free_filespec_data(p->one);
 			diff_free_filespec_data(p->two);
 		} else if (DIFF_FILE_VALID(p->one)) {
-			diff_populate_filespec(p->one, 1);
+			diff_populate_filespec(p->one, CHECK_SIZE_ONLY);
 			copied = added = 0;
 			diff_free_filespec_data(p->one);
 		} else if (DIFF_FILE_VALID(p->two)) {
-			diff_populate_filespec(p->two, 1);
+			diff_populate_filespec(p->two, CHECK_SIZE_ONLY);
 			copied = 0;
 			added = p->two->size;
 			diff_free_filespec_data(p->two);
@@ -2091,7 +2147,6 @@ static unsigned char *deflate_it(char *data,
 	unsigned char *deflated;
 	git_zstream stream;
 
-	memset(&stream, 0, sizeof(stream));
 	git_deflate_init(&stream, zlib_compression_level);
 	bound = git_deflate_bound(&stream, size);
 	deflated = xmalloc(bound);
@@ -2185,8 +2240,8 @@ int diff_filespec_is_binary(struct diff_filespec *one)
 			one->is_binary = one->driver->binary;
 		else {
 			if (!one->data && DIFF_FILE_VALID(one))
-				diff_populate_filespec(one, 0);
-			if (one->data)
+				diff_populate_filespec(one, CHECK_BINARY);
+			if (one->is_binary == -1 && one->data)
 				one->is_binary = buffer_is_binary(one->data,
 						one->size);
 			if (one->is_binary == -1)
@@ -2321,6 +2376,19 @@ static void builtin_diff(const char *name_a,
 	} else if (!DIFF_OPT_TST(o, TEXT) &&
 	    ( (!textconv_one && diff_filespec_is_binary(one)) ||
 	      (!textconv_two && diff_filespec_is_binary(two)) )) {
+		if (!one->data && !two->data &&
+		    S_ISREG(one->mode) && S_ISREG(two->mode) &&
+		    !DIFF_OPT_TST(o, BINARY)) {
+			if (!hashcmp(one->sha1, two->sha1)) {
+				if (must_show_header)
+					fprintf(o->file, "%s", header.buf);
+				goto free_ab_and_return;
+			}
+			fprintf(o->file, "%s", header.buf);
+			fprintf(o->file, "%sBinary files %s and %s differ\n",
+				line_prefix, lbl[0], lbl[1]);
+			goto free_ab_and_return;
+		}
 		if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
 			die("unable to read files to diff");
 		/* Quite common confusing case */
@@ -2341,6 +2409,7 @@ static void builtin_diff(const char *name_a,
 	} else {
 		/* Crazy xdl interfaces.. */
 		const char *diffopts = getenv("GIT_DIFF_OPTS");
+		const char *v;
 		xpparam_t xpp;
 		xdemitconf_t xecfg;
 		struct emit_callback ecbdata;
@@ -2379,14 +2448,15 @@ static void builtin_diff(const char *name_a,
 			xdiff_set_find_func(&xecfg, pe->pattern, pe->cflags);
 		if (!diffopts)
 			;
-		else if (starts_with(diffopts, "--unified="))
-			xecfg.ctxlen = strtoul(diffopts + 10, NULL, 10);
-		else if (starts_with(diffopts, "-u"))
-			xecfg.ctxlen = strtoul(diffopts + 2, NULL, 10);
+		else if (skip_prefix(diffopts, "--unified=", &v))
+			xecfg.ctxlen = strtoul(v, NULL, 10);
+		else if (skip_prefix(diffopts, "-u", &v))
+			xecfg.ctxlen = strtoul(v, NULL, 10);
 		if (o->word_diff)
 			init_diff_words_data(&ecbdata, o, one, two);
-		xdi_diff_outf(&mf1, &mf2, fn_out_consume, &ecbdata,
-			      &xpp, &xecfg);
+		if (xdi_diff_outf(&mf1, &mf2, fn_out_consume, &ecbdata,
+				  &xpp, &xecfg))
+			die("unable to generate diff for %s", one->path);
 		if (o->word_diff)
 			free_diff_words_data(&ecbdata);
 		if (textconv_one)
@@ -2463,8 +2533,9 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 		xpp.flags = o->xdl_opts;
 		xecfg.ctxlen = o->context;
 		xecfg.interhunkctxlen = o->interhunkcontext;
-		xdi_diff_outf(&mf1, &mf2, diffstat_consume, diffstat,
-			      &xpp, &xecfg);
+		if (xdi_diff_outf(&mf1, &mf2, diffstat_consume, diffstat,
+				  &xpp, &xecfg))
+			die("unable to generate diffstat for %s", one->path);
 	}
 
 	diff_free_filespec_data(one);
@@ -2510,8 +2581,9 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 		memset(&xecfg, 0, sizeof(xecfg));
 		xecfg.ctxlen = 1; /* at least one context line */
 		xpp.flags = 0;
-		xdi_diff_outf(&mf1, &mf2, checkdiff_consume, &data,
-			      &xpp, &xecfg);
+		if (xdi_diff_outf(&mf1, &mf2, checkdiff_consume, &data,
+				  &xpp, &xecfg))
+			die("unable to generate checkdiff for %s", one->path);
 
 		if (data.ws_rule & WS_BLANK_AT_EOF) {
 			struct emit_callback ecbdata;
@@ -2540,12 +2612,9 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 
 struct diff_filespec *alloc_filespec(const char *path)
 {
-	int namelen = strlen(path);
-	struct diff_filespec *spec = xmalloc(sizeof(*spec) + namelen + 1);
+	struct diff_filespec *spec;
 
-	memset(spec, 0, sizeof(*spec));
-	spec->path = (char *)(spec + 1);
-	memcpy(spec->path, path, namelen+1);
+	FLEXPTR_ALLOC_STR(spec, path, path);
 	spec->count = 1;
 	spec->is_binary = -1;
 	return spec;
@@ -2640,21 +2709,21 @@ static int reuse_worktree_file(const char *name, const unsigned char *sha1, int
 
 static int diff_populate_gitlink(struct diff_filespec *s, int size_only)
 {
-	int len;
-	char *data = xmalloc(100), *dirty = "";
+	struct strbuf buf = STRBUF_INIT;
+	char *dirty = "";
 
 	/* Are we looking at the work tree? */
 	if (s->dirty_submodule)
 		dirty = "-dirty";
 
-	len = snprintf(data, 100,
-		       "Subproject commit %s%s\n", sha1_to_hex(s->sha1), dirty);
-	s->data = data;
-	s->size = len;
-	s->should_free = 1;
+	strbuf_addf(&buf, "Subproject commit %s%s\n", sha1_to_hex(s->sha1), dirty);
+	s->size = buf.len;
 	if (size_only) {
 		s->data = NULL;
-		free(data);
+		strbuf_release(&buf);
+	} else {
+		s->data = strbuf_detach(&buf, NULL);
+		s->should_free = 1;
 	}
 	return 0;
 }
@@ -2664,8 +2733,9 @@ static int diff_populate_gitlink(struct diff_filespec *s, int size_only)
  * grab the data for the blob (or file) for our own in-core comparison.
  * diff_filespec has data and size fields for this purpose.
  */
-int diff_populate_filespec(struct diff_filespec *s, int size_only)
+int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
 {
+	int size_only = flags & CHECK_SIZE_ONLY;
 	int err = 0;
 	/*
 	 * demote FAIL to WARN to allow inspecting the situation
@@ -2720,6 +2790,11 @@ int diff_populate_filespec(struct diff_filespec *s, int size_only)
 		}
 		if (size_only)
 			return 0;
+		if ((flags & CHECK_BINARY) &&
+		    s->size > big_file_threshold && s->is_binary == -1) {
+			s->is_binary = 1;
+			return 0;
+		}
 		fd = open(s->path, O_RDONLY);
 		if (fd < 0)
 			goto err_empty;
@@ -2741,16 +2816,21 @@ int diff_populate_filespec(struct diff_filespec *s, int size_only)
 	}
 	else {
 		enum object_type type;
-		if (size_only) {
+		if (size_only || (flags & CHECK_BINARY)) {
 			type = sha1_object_info(s->sha1, &s->size);
 			if (type < 0)
 				die("unable to read %s", sha1_to_hex(s->sha1));
-		} else {
-			s->data = read_sha1_file(s->sha1, &type, &s->size);
-			if (!s->data)
-				die("unable to read %s", sha1_to_hex(s->sha1));
-			s->should_free = 1;
+			if (size_only)
+				return 0;
+			if (s->size > big_file_threshold && s->is_binary == -1) {
+				s->is_binary = 1;
+				return 0;
+			}
 		}
+		s->data = read_sha1_file(s->sha1, &type, &s->size);
+		if (!s->data)
+			die("unable to read %s", sha1_to_hex(s->sha1));
+		s->should_free = 1;
 	}
 	return 0;
 }
@@ -2791,8 +2871,7 @@ static void prep_temp_blob(const char *path, struct diff_tempfile *temp,
 	strbuf_addstr(&template, "XXXXXX_");
 	strbuf_addstr(&template, base);
 
-	fd = git_mkstemps(temp->tmp_path, PATH_MAX, template.buf,
-			strlen(base) + 1);
+	fd = mks_tempfile_ts(&temp->tempfile, template.buf, strlen(base) + 1);
 	if (fd < 0)
 		die_errno("unable to create temp-file");
 	if (convert_to_working_tree(path,
@@ -2802,11 +2881,10 @@ static void prep_temp_blob(const char *path, struct diff_tempfile *temp,
 	}
 	if (write_in_full(fd, blob, size) != size)
 		die_errno("unable to write temp-file");
-	close(fd);
-	temp->name = temp->tmp_path;
-	strcpy(temp->hex, sha1_to_hex(sha1));
-	temp->hex[40] = 0;
-	sprintf(temp->mode, "%06o", mode);
+	close_tempfile(&temp->tempfile);
+	temp->name = get_tempfile_path(&temp->tempfile);
+	sha1_to_hex_r(temp->hex, sha1);
+	xsnprintf(temp->mode, sizeof(temp->mode), "%06o", mode);
 	strbuf_release(&buf);
 	strbuf_release(&template);
 	free(path_dup);
@@ -2823,17 +2901,11 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 		 * a '+' entry produces this for file-1.
 		 */
 		temp->name = "/dev/null";
-		strcpy(temp->hex, ".");
-		strcpy(temp->mode, ".");
+		xsnprintf(temp->hex, sizeof(temp->hex), ".");
+		xsnprintf(temp->mode, sizeof(temp->mode), ".");
 		return temp;
 	}
 
-	if (!remove_tempfile_installed) {
-		atexit(remove_tempfile);
-		sigchain_push_common(remove_tempfile_on_signal);
-		remove_tempfile_installed = 1;
-	}
-
 	if (!S_ISGITLINK(one->mode) &&
 	    (!one->sha1_valid ||
 	     reuse_worktree_file(name, one->sha1, 1))) {
@@ -2858,16 +2930,16 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 			/* we can borrow from the file in the work tree */
 			temp->name = name;
 			if (!one->sha1_valid)
-				strcpy(temp->hex, sha1_to_hex(null_sha1));
+				sha1_to_hex_r(temp->hex, null_sha1);
 			else
-				strcpy(temp->hex, sha1_to_hex(one->sha1));
+				sha1_to_hex_r(temp->hex, one->sha1);
 			/* Even though we may sometimes borrow the
 			 * contents from the work tree, we always want
 			 * one->mode.  mode is trustworthy even when
 			 * !(one->sha1_valid), as long as
 			 * DIFF_FILE_VALID(one).
 			 */
-			sprintf(temp->mode, "%06o", one->mode);
+			xsnprintf(temp->mode, sizeof(temp->mode), "%06o", one->mode);
 		}
 		return temp;
 	}
@@ -2880,6 +2952,16 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 	return temp;
 }
 
+static void add_external_diff_name(struct argv_array *argv,
+				   const char *name,
+				   struct diff_filespec *df)
+{
+	struct diff_tempfile *temp = prepare_temp_file(name, df);
+	argv_array_push(argv, temp->name);
+	argv_array_push(argv, temp->hex);
+	argv_array_push(argv, temp->mode);
+}
+
 /* An external diff command takes:
  *
  * diff-cmd name infile1 infile1-sha1 infile1-mode \
@@ -2896,48 +2978,32 @@ static void run_external_diff(const char *pgm,
 			      struct diff_options *o)
 {
 	struct argv_array argv = ARGV_ARRAY_INIT;
-	int retval;
+	struct argv_array env = ARGV_ARRAY_INIT;
 	struct diff_queue_struct *q = &diff_queued_diff;
-	const char *env[3] = { NULL };
-	char env_counter[50];
-	char env_total[50];
+
+	argv_array_push(&argv, pgm);
+	argv_array_push(&argv, name);
 
 	if (one && two) {
-		struct diff_tempfile *temp_one, *temp_two;
-		const char *othername = (other ? other : name);
-		temp_one = prepare_temp_file(name, one);
-		temp_two = prepare_temp_file(othername, two);
-		argv_array_push(&argv, pgm);
-		argv_array_push(&argv, name);
-		argv_array_push(&argv, temp_one->name);
-		argv_array_push(&argv, temp_one->hex);
-		argv_array_push(&argv, temp_one->mode);
-		argv_array_push(&argv, temp_two->name);
-		argv_array_push(&argv, temp_two->hex);
-		argv_array_push(&argv, temp_two->mode);
-		if (other) {
+		add_external_diff_name(&argv, name, one);
+		if (!other)
+			add_external_diff_name(&argv, name, two);
+		else {
+			add_external_diff_name(&argv, other, two);
 			argv_array_push(&argv, other);
 			argv_array_push(&argv, xfrm_msg);
 		}
-	} else {
-		argv_array_push(&argv, pgm);
-		argv_array_push(&argv, name);
 	}
-	fflush(NULL);
 
-	env[0] = env_counter;
-	snprintf(env_counter, sizeof(env_counter), "GIT_DIFF_PATH_COUNTER=%d",
-		 ++o->diff_path_counter);
-	env[1] = env_total;
-	snprintf(env_total, sizeof(env_total), "GIT_DIFF_PATH_TOTAL=%d", q->nr);
+	argv_array_pushf(&env, "GIT_DIFF_PATH_COUNTER=%d", ++o->diff_path_counter);
+	argv_array_pushf(&env, "GIT_DIFF_PATH_TOTAL=%d", q->nr);
+
+	if (run_command_v_opt_cd_env(argv.argv, RUN_USING_SHELL, NULL, env.argv))
+		die(_("external diff died, stopping at %s"), name);
 
-	retval = run_command_v_opt_cd_env(argv.argv, RUN_USING_SHELL, NULL, env);
 	remove_tempfile();
 	argv_array_clear(&argv);
-	if (retval) {
-		fprintf(stderr, "external diff died, stopping at %s.\n", name);
-		exit(1);
-	}
+	argv_array_clear(&env);
 }
 
 static int similarity_index(struct diff_filepair *p)
@@ -3203,8 +3269,10 @@ void diff_setup(struct diff_options *options)
 	options->rename_limit = -1;
 	options->dirstat_permille = diff_dirstat_permille_default;
 	options->context = diff_context_default;
+	options->ws_error_highlight = WSEH_NEW;
 	DIFF_OPT_SET(options, RENAME_EMPTY);
 
+	/* pathchange left =NULL by default */
 	options->change = diff_change;
 	options->add_remove = diff_addremove;
 	options->use_color = diff_use_color_default;
@@ -3396,12 +3464,10 @@ int parse_long_opt(const char *opt, const char **argv,
 		   const char **optarg)
 {
 	const char *arg = argv[0];
-	if (arg[0] != '-' || arg[1] != '-')
+	if (!skip_prefix(arg, "--", &arg))
 		return 0;
-	arg += strlen("--");
-	if (!starts_with(arg, opt))
+	if (!skip_prefix(arg, opt, &arg))
 		return 0;
-	arg += strlen(opt);
 	if (*arg == '=') { /* stuck form: --option=value */
 		*optarg = arg + 1;
 		return 1;
@@ -3425,13 +3491,13 @@ static int stat_opt(struct diff_options *options, const char **av)
 	int count = options->stat_count;
 	int argcount = 1;
 
-	arg += strlen("--stat");
+	if (!skip_prefix(arg, "--stat", &arg))
+		die("BUG: stat option does not begin with --stat: %s", arg);
 	end = (char *)arg;
 
 	switch (*arg) {
 	case '-':
-		if (starts_with(arg, "-width")) {
-			arg += strlen("-width");
+		if (skip_prefix(arg, "-width", &arg)) {
 			if (*arg == '=')
 				width = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3440,8 +3506,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 				width = strtoul(av[1], &end, 10);
 				argcount = 2;
 			}
-		} else if (starts_with(arg, "-name-width")) {
-			arg += strlen("-name-width");
+		} else if (skip_prefix(arg, "-name-width", &arg)) {
 			if (*arg == '=')
 				name_width = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3450,8 +3515,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 				name_width = strtoul(av[1], &end, 10);
 				argcount = 2;
 			}
-		} else if (starts_with(arg, "-graph-width")) {
-			arg += strlen("-graph-width");
+		} else if (skip_prefix(arg, "-graph-width", &arg)) {
 			if (*arg == '=')
 				graph_width = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3460,8 +3524,7 @@ static int stat_opt(struct diff_options *options, const char **av)
 				graph_width = strtoul(av[1], &end, 10);
 				argcount = 2;
 			}
-		} else if (starts_with(arg, "-count")) {
-			arg += strlen("-count");
+		} else if (skip_prefix(arg, "-count", &arg)) {
 			if (*arg == '=')
 				count = strtoul(arg + 1, &end, 10);
 			else if (!*arg && !av[1])
@@ -3593,12 +3656,55 @@ static void enable_patch_output(int *fmt) {
 	*fmt |= DIFF_FORMAT_PATCH;
 }
 
-int diff_opt_parse(struct diff_options *options, const char **av, int ac)
+static int parse_one_token(const char **arg, const char *token)
+{
+	const char *rest;
+	if (skip_prefix(*arg, token, &rest) && (!*rest || *rest == ',')) {
+		*arg = rest;
+		return 1;
+	}
+	return 0;
+}
+
+static int parse_ws_error_highlight(struct diff_options *opt, const char *arg)
+{
+	const char *orig_arg = arg;
+	unsigned val = 0;
+	while (*arg) {
+		if (parse_one_token(&arg, "none"))
+			val = 0;
+		else if (parse_one_token(&arg, "default"))
+			val = WSEH_NEW;
+		else if (parse_one_token(&arg, "all"))
+			val = WSEH_NEW | WSEH_OLD | WSEH_CONTEXT;
+		else if (parse_one_token(&arg, "new"))
+			val |= WSEH_NEW;
+		else if (parse_one_token(&arg, "old"))
+			val |= WSEH_OLD;
+		else if (parse_one_token(&arg, "context"))
+			val |= WSEH_CONTEXT;
+		else {
+			error("unknown value after ws-error-highlight=%.*s",
+			      (int)(arg - orig_arg), orig_arg);
+			return 0;
+		}
+		if (*arg)
+			arg++;
+	}
+	opt->ws_error_highlight = val;
+	return 1;
+}
+
+int diff_opt_parse(struct diff_options *options,
+		   const char **av, int ac, const char *prefix)
 {
 	const char *arg = av[0];
 	const char *optarg;
 	int argcount;
 
+	if (!prefix)
+		prefix = "";
+
 	/* Output format options */
 	if (!strcmp(arg, "-p") || !strcmp(arg, "-u") || !strcmp(arg, "--patch")
 	    || opt_arg(arg, 'U', "unified", &options->context))
@@ -3614,17 +3720,17 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		options->output_format |= DIFF_FORMAT_SHORTSTAT;
 	else if (!strcmp(arg, "-X") || !strcmp(arg, "--dirstat"))
 		return parse_dirstat_opt(options, "");
-	else if (starts_with(arg, "-X"))
-		return parse_dirstat_opt(options, arg + 2);
-	else if (starts_with(arg, "--dirstat="))
-		return parse_dirstat_opt(options, arg + 10);
+	else if (skip_prefix(arg, "-X", &arg))
+		return parse_dirstat_opt(options, arg);
+	else if (skip_prefix(arg, "--dirstat=", &arg))
+		return parse_dirstat_opt(options, arg);
 	else if (!strcmp(arg, "--cumulative"))
 		return parse_dirstat_opt(options, "cumulative");
 	else if (!strcmp(arg, "--dirstat-by-file"))
 		return parse_dirstat_opt(options, "files");
-	else if (starts_with(arg, "--dirstat-by-file=")) {
+	else if (skip_prefix(arg, "--dirstat-by-file=", &arg)) {
 		parse_dirstat_opt(options, "files");
-		return parse_dirstat_opt(options, arg + 18);
+		return parse_dirstat_opt(options, arg);
 	}
 	else if (!strcmp(arg, "--check"))
 		options->output_format |= DIFF_FORMAT_CHECKDIFF;
@@ -3674,9 +3780,9 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_OPT_CLR(options, RENAME_EMPTY);
 	else if (!strcmp(arg, "--relative"))
 		DIFF_OPT_SET(options, RELATIVE_NAME);
-	else if (starts_with(arg, "--relative=")) {
+	else if (skip_prefix(arg, "--relative=", &arg)) {
 		DIFF_OPT_SET(options, RELATIVE_NAME);
-		options->prefix = arg + 11;
+		options->prefix = arg;
 	}
 
 	/* xdiff options */
@@ -3723,12 +3829,13 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_OPT_SET(options, FIND_COPIES_HARDER);
 	else if (!strcmp(arg, "--follow"))
 		DIFF_OPT_SET(options, FOLLOW_RENAMES);
-	else if (!strcmp(arg, "--no-follow"))
+	else if (!strcmp(arg, "--no-follow")) {
 		DIFF_OPT_CLR(options, FOLLOW_RENAMES);
-	else if (!strcmp(arg, "--color"))
+		DIFF_OPT_CLR(options, DEFAULT_FOLLOW_RENAMES);
+	} else if (!strcmp(arg, "--color"))
 		options->use_color = 1;
-	else if (starts_with(arg, "--color=")) {
-		int value = git_config_colorbool(NULL, arg+8);
+	else if (skip_prefix(arg, "--color=", &arg)) {
+		int value = git_config_colorbool(NULL, arg);
 		if (value < 0)
 			return error("option `color' expects \"always\", \"auto\", or \"never\"");
 		options->use_color = value;
@@ -3739,29 +3846,28 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		options->use_color = 1;
 		options->word_diff = DIFF_WORDS_COLOR;
 	}
-	else if (starts_with(arg, "--color-words=")) {
+	else if (skip_prefix(arg, "--color-words=", &arg)) {
 		options->use_color = 1;
 		options->word_diff = DIFF_WORDS_COLOR;
-		options->word_regex = arg + 14;
+		options->word_regex = arg;
 	}
 	else if (!strcmp(arg, "--word-diff")) {
 		if (options->word_diff == DIFF_WORDS_NONE)
 			options->word_diff = DIFF_WORDS_PLAIN;
 	}
-	else if (starts_with(arg, "--word-diff=")) {
-		const char *type = arg + 12;
-		if (!strcmp(type, "plain"))
+	else if (skip_prefix(arg, "--word-diff=", &arg)) {
+		if (!strcmp(arg, "plain"))
 			options->word_diff = DIFF_WORDS_PLAIN;
-		else if (!strcmp(type, "color")) {
+		else if (!strcmp(arg, "color")) {
 			options->use_color = 1;
 			options->word_diff = DIFF_WORDS_COLOR;
 		}
-		else if (!strcmp(type, "porcelain"))
+		else if (!strcmp(arg, "porcelain"))
 			options->word_diff = DIFF_WORDS_PORCELAIN;
-		else if (!strcmp(type, "none"))
+		else if (!strcmp(arg, "none"))
 			options->word_diff = DIFF_WORDS_NONE;
 		else
-			die("bad --word-diff argument: %s", type);
+			die("bad --word-diff argument: %s", arg);
 	}
 	else if ((argcount = parse_long_opt("word-diff-regex", av, &optarg))) {
 		if (options->word_diff == DIFF_WORDS_NONE)
@@ -3784,13 +3890,15 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--ignore-submodules")) {
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
 		handle_ignore_submodules_arg(options, "all");
-	} else if (starts_with(arg, "--ignore-submodules=")) {
+	} else if (skip_prefix(arg, "--ignore-submodules=", &arg)) {
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
-		handle_ignore_submodules_arg(options, arg + 20);
+		handle_ignore_submodules_arg(options, arg);
 	} else if (!strcmp(arg, "--submodule"))
 		DIFF_OPT_SET(options, SUBMODULE_LOG);
-	else if (starts_with(arg, "--submodule="))
-		return parse_submodule_opt(options, arg + 12);
+	else if (skip_prefix(arg, "--submodule=", &arg))
+		return parse_submodule_opt(options, arg);
+	else if (skip_prefix(arg, "--ws-error-highlight=", &arg))
+		return parse_ws_error_highlight(options, arg);
 
 	/* misc options */
 	else if (!strcmp(arg, "-z"))
@@ -3813,7 +3921,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--pickaxe-regex"))
 		options->pickaxe_opts |= DIFF_PICKAXE_REGEX;
 	else if ((argcount = short_opt('O', av, &optarg))) {
-		options->orderfile = optarg;
+		const char *path = prefix_filename(prefix, strlen(prefix), optarg);
+		options->orderfile = xstrdup(path);
 		return argcount;
 	}
 	else if ((argcount = parse_long_opt("diff-filter", av, &optarg))) {
@@ -3825,8 +3934,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	}
 	else if (!strcmp(arg, "--abbrev"))
 		options->abbrev = DEFAULT_ABBREV;
-	else if (starts_with(arg, "--abbrev=")) {
-		options->abbrev = strtoul(arg + 9, NULL, 10);
+	else if (skip_prefix(arg, "--abbrev=", &arg)) {
+		options->abbrev = strtoul(arg, NULL, 10);
 		if (options->abbrev < MINIMUM_ABBREV)
 			options->abbrev = MINIMUM_ABBREV;
 		else if (40 < options->abbrev)
@@ -3852,9 +3961,10 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--no-function-context"))
 		DIFF_OPT_CLR(options, FUNCCONTEXT);
 	else if ((argcount = parse_long_opt("output", av, &optarg))) {
-		options->file = fopen(optarg, "w");
+		const char *path = prefix_filename(prefix, strlen(prefix), optarg);
+		options->file = fopen(path, "w");
 		if (!options->file)
-			die_errno("Could not open '%s'", optarg);
+			die_errno("Could not open '%s'", path);
 		options->close_file = 1;
 		return argcount;
 	} else
@@ -3907,16 +4017,13 @@ static int diff_scoreopt_parse(const char *opt)
 	cmd = *opt++;
 	if (cmd == '-') {
 		/* convert the long-form arguments into short-form versions */
-		if (starts_with(opt, "break-rewrites")) {
-			opt += strlen("break-rewrites");
+		if (skip_prefix(opt, "break-rewrites", &opt)) {
 			if (*opt == 0 || *opt++ == '=')
 				cmd = 'B';
-		} else if (starts_with(opt, "find-copies")) {
-			opt += strlen("find-copies");
+		} else if (skip_prefix(opt, "find-copies", &opt)) {
 			if (*opt == 0 || *opt++ == '=')
 				cmd = 'C';
-		} else if (starts_with(opt, "find-renames")) {
-			opt += strlen("find-renames");
+		} else if (skip_prefix(opt, "find-renames", &opt)) {
 			if (*opt == 0 || *opt++ == '=')
 				cmd = 'M';
 		}
@@ -3984,9 +4091,9 @@ const char *diff_unique_abbrev(const unsigned char *sha1, int len)
 	if (abblen < 37) {
 		static char hex[41];
 		if (len < abblen && abblen <= len + 2)
-			sprintf(hex, "%s%.*s", abbrev, len+3-abblen, "..");
+			xsnprintf(hex, sizeof(hex), "%s%.*s", abbrev, len+3-abblen, "..");
 		else
-			sprintf(hex, "%s...", abbrev);
+			xsnprintf(hex, sizeof(hex), "%s...", abbrev);
 		return hex;
 	}
 	return sha1_to_hex(sha1);
@@ -4413,8 +4520,10 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
 		xpp.flags = 0;
 		xecfg.ctxlen = 3;
 		xecfg.flags = 0;
-		xdi_diff_outf(&mf1, &mf2, patch_id_consume, &data,
-			      &xpp, &xecfg);
+		if (xdi_diff_outf(&mf1, &mf2, patch_id_consume, &data,
+				  &xpp, &xecfg))
+			return error("unable to generate patch-id diff for %s",
+				     p->one->path);
 	}
 
 	git_SHA1_Final(sha1, &ctx);
@@ -4528,7 +4637,7 @@ void diff_flush(struct diff_options *options)
 			show_stats(&diffstat, options);
 		if (output_format & DIFF_FORMAT_SHORTSTAT)
 			show_shortstats(&diffstat, options);
-		if (output_format & DIFF_FORMAT_DIRSTAT)
+		if (output_format & DIFF_FORMAT_DIRSTAT && dirstat_by_line)
 			show_dirstat_by_line(&diffstat, options);
 		free_diffstat_info(&diffstat);
 		separator++;
@@ -4698,8 +4807,8 @@ static int diff_filespec_check_stat_unmatch(struct diff_filepair *p)
 	    !DIFF_FILE_VALID(p->two) ||
 	    (p->one->sha1_valid && p->two->sha1_valid) ||
 	    (p->one->mode != p->two->mode) ||
-	    diff_populate_filespec(p->one, 1) ||
-	    diff_populate_filespec(p->two, 1) ||
+	    diff_populate_filespec(p->one, CHECK_SIZE_ONLY) ||
+	    diff_populate_filespec(p->two, CHECK_SIZE_ONLY) ||
 	    (p->one->size != p->two->size) ||
 	    !diff_filespec_is_identical(p->one, p->two)) /* (2) */
 		p->skip_stat_unmatch_result = 1;
@@ -4752,6 +4861,7 @@ void diffcore_fix_diff_index(struct diff_options *options)
 
 void diffcore_std(struct diff_options *options)
 {
+	/* NOTE please keep the following in sync with diff_tree_combined() */
 	if (options->skip_stat_unmatch)
 		diffcore_skip_stat_unmatch(options);
 	if (!options->found_follow) {
@@ -4940,7 +5050,7 @@ static char *run_textconv(const char *pgm, struct diff_filespec *spec,
 	struct diff_tempfile *temp;
 	const char *argv[3];
 	const char **arg = argv;
-	struct child_process child;
+	struct child_process child = CHILD_PROCESS_INIT;
 	struct strbuf buf = STRBUF_INIT;
 	int err = 0;
 
@@ -4949,7 +5059,6 @@ static char *run_textconv(const char *pgm, struct diff_filespec *spec,
 	*arg++ = temp->name;
 	*arg = NULL;
 
-	memset(&child, 0, sizeof(child));
 	child.use_shell = 1;
 	child.argv = argv;
 	child.out = -1;
@@ -4978,7 +5087,7 @@ size_t fill_textconv(struct userdiff_driver *driver,
 {
 	size_t size;
 
-	if (!driver || !driver->textconv) {
+	if (!driver) {
 		if (!DIFF_FILE_VALID(df)) {
 			*outbuf = "";
 			return 0;
@@ -4989,6 +5098,9 @@ size_t fill_textconv(struct userdiff_driver *driver,
 		return df->size;
 	}
 
+	if (!driver->textconv)
+		die("BUG: fill_textconv called with non-textconv driver");
+
 	if (driver->textconv_cache && df->sha1_valid) {
 		*outbuf = notes_cache_get(driver->textconv_cache, df->sha1,
 					  &size);