patch, 5 partsdiff --ignore-case

diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 00d36c3..70c8b87 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -36,11 +36,6 @@ extern "C" {
 #define XDF_HISTOGRAM_DIFF (1 << 6)
 #define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | XDF_IGNORE_WHITESPACE_CHANGE | XDF_IGNORE_WHITESPACE_AT_EOL)
 
-#define XDL_PATCH_NORMAL '-'
-#define XDL_PATCH_REVERSE '+'
-#define XDL_PATCH_MODEMASK ((1 << 8) - 1)
-#define XDL_PATCH_IGNOREBSPACE (1 << 8)
-
 #define XDL_EMIT_FUNCNAMES (1 << 0)
 #define XDL_EMIT_COMMON (1 << 1)
 #define XDL_EMIT_FUNCCONTEXT (1 << 2)

diff.c, diff.h, merge-recursive.c, xdiff/xdiff.h, xdiff/xdiffi.c, xdiff/xhistogram.c, xdiff/xpatience.c, xdiff/xprepare.c

diff --git a/diff.c b/diff.c
index 374ecf3..52cda7a 100644
--- a/diff.c
+++ b/diff.c
@@ -3400,9 +3400,9 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--ignore-space-at-eol"))
 		DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
 	else if (!strcmp(arg, "--patience"))
-		DIFF_XDL_SET(options, PATIENCE_DIFF);
+		options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
 	else if (!strcmp(arg, "--histogram"))
-		DIFF_XDL_SET(options, HISTOGRAM_DIFF);
+		options->xdl_opts = DIFF_WITH_ALG(options, HISTOGRAM_DIFF);
 
 	/* flags options */
 	else if (!strcmp(arg, "--binary")) {
diff --git a/diff.h b/diff.h
index 0c51724..e688a48 100644
--- a/diff.h
+++ b/diff.h
@@ -88,6 +88,8 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_XDL_SET(opts, flag)    ((opts)->xdl_opts |= XDF_##flag)
 #define DIFF_XDL_CLR(opts, flag)    ((opts)->xdl_opts &= ~XDF_##flag)
 
+#define DIFF_WITH_ALG(opts, flag)   (((opts)->xdl_opts & ~XDF_DIFF_ALGORITHM_MASK) | XDF_##flag)
+
 enum diff_words_type {
 	DIFF_WORDS_NONE = 0,
 	DIFF_WORDS_PORCELAIN,
diff --git a/merge-recursive.c b/merge-recursive.c
index cc664c3..1d574fe 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -2069,9 +2069,9 @@ int parse_merge_opt(struct merge_options *o, const char *s)
 	else if (!prefixcmp(s, "subtree="))
 		o->subtree_shift = s + strlen("subtree=");
 	else if (!strcmp(s, "patience"))
-		o->xdl_opts |= XDF_PATIENCE_DIFF;
+		o->xdl_opts = DIFF_WITH_ALG(o, PATIENCE_DIFF);
 	else if (!strcmp(s, "histogram"))
-		o->xdl_opts |= XDF_HISTOGRAM_DIFF;
+		o->xdl_opts = DIFF_WITH_ALG(o, HISTOGRAM_DIFF);
 	else if (!strcmp(s, "ignore-space-change"))
 		o->xdl_opts |= XDF_IGNORE_WHITESPACE_CHANGE;
 	else if (!strcmp(s, "ignore-all-space"))
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 70c8b87..09215af 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -32,9 +32,12 @@ extern "C" {
 #define XDF_IGNORE_WHITESPACE (1 << 2)
 #define XDF_IGNORE_WHITESPACE_CHANGE (1 << 3)
 #define XDF_IGNORE_WHITESPACE_AT_EOL (1 << 4)
+#define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | XDF_IGNORE_WHITESPACE_CHANGE | XDF_IGNORE_WHITESPACE_AT_EOL)
+
 #define XDF_PATIENCE_DIFF (1 << 5)
 #define XDF_HISTOGRAM_DIFF (1 << 6)
-#define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | XDF_IGNORE_WHITESPACE_CHANGE | XDF_IGNORE_WHITESPACE_AT_EOL)
+#define XDF_DIFF_ALGORITHM_MASK (XDF_PATIENCE_DIFF | XDF_HISTOGRAM_DIFF)
+#define XDF_DIFF_ALG(x) ((x) & XDF_DIFF_ALGORITHM_MASK)
 
 #define XDL_EMIT_FUNCNAMES (1 << 0)
 #define XDL_EMIT_COMMON (1 << 1)
diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index 75a3922..bc889e8 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -328,10 +328,10 @@ int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 	xdalgoenv_t xenv;
 	diffdata_t dd1, dd2;
 
-	if (xpp->flags & XDF_PATIENCE_DIFF)
+	if (XDF_DIFF_ALG(xpp->flags) == XDF_PATIENCE_DIFF)
 		return xdl_do_patience_diff(mf1, mf2, xpp, xe);
 
-	if (xpp->flags & XDF_HISTOGRAM_DIFF)
+	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
 		return xdl_do_histogram_diff(mf1, mf2, xpp, xe);
 
 	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index 18f6f99..bf99787 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -252,7 +252,7 @@ static int fall_back_to_classic_diff(struct histindex *index,
 		int line1, int count1, int line2, int count2)
 {
 	xpparam_t xpp;
-	xpp.flags = index->xpp->flags & ~XDF_HISTOGRAM_DIFF;
+	xpp.flags = index->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
 
 	return xdl_fall_back_diff(index->env, &xpp,
 				  line1, count1, line2, count2);
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index fdd7d02..04e1a1a 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -288,7 +288,7 @@ static int fall_back_to_classic_diff(struct hashmap *map,
 		int line1, int count1, int line2, int count2)
 {
 	xpparam_t xpp;
-	xpp.flags = map->xpp->flags & ~XDF_PATIENCE_DIFF;
+	xpp.flags = map->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
 
 	return xdl_fall_back_diff(map->env, &xpp,
 				  line1, count1, line2, count2);
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index e419f4f..63a22c6 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -181,7 +181,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 	if (!(recs = (xrecord_t **) xdl_malloc(narec * sizeof(xrecord_t *))))
 		goto abort;
 
-	if (xpp->flags & XDF_HISTOGRAM_DIFF)
+	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
 		hbits = hsize = 0;
 	else {
 		hbits = xdl_hashbits((unsigned int) narec);
@@ -209,8 +209,8 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 			crec->ha = hav;
 			recs[nrec++] = crec;
 
-			if (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
-				xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
+			if ((XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
+			    xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
 				goto abort;
 		}
 	}
@@ -273,16 +273,15 @@ int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 	 * (nrecs) will be updated correctly anyway by
 	 * xdl_prepare_ctx().
 	 */
-	sample = xpp->flags & XDF_HISTOGRAM_DIFF ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1;
+	sample = (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF
+		  ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1);
 
 	enl1 = xdl_guess_lines(mf1, sample) + 1;
 	enl2 = xdl_guess_lines(mf2, sample) + 1;
 
-	if (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
-		xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0) {
-
+	if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF &&
+	    xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
 		return -1;
-	}
 
 	if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
 
@@ -296,9 +295,9 @@ int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 		return -1;
 	}
 
-	if (!(xpp->flags & XDF_PATIENCE_DIFF) &&
-			!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
-			xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
+	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
+	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
+	    xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
 
 		xdl_free_ctx(&xe->xdf2);
 		xdl_free_ctx(&xe->xdf1);

diff.c, xdiff/xdiff.h, xdiff/xutils.c

diff --git a/diff.c b/diff.c
index 52cda7a..87b2ec1 100644
--- a/diff.c
+++ b/diff.c
@@ -2142,7 +2142,7 @@ static void builtin_diff(const char *name_a,
 		struct emit_callback ecbdata;
 		const struct userdiff_funcname *pe;
 
-		if (!DIFF_XDL_TST(o, WHITESPACE_FLAGS) || must_show_header) {
+		if (!DIFF_XDL_TST(o, INEXACT_MATCH) || must_show_header) {
 			fprintf(o->file, "%s", header.buf);
 			strbuf_reset(&header);
 		}
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 09215af..48793f9 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -32,7 +32,11 @@ extern "C" {
 #define XDF_IGNORE_WHITESPACE (1 << 2)
 #define XDF_IGNORE_WHITESPACE_CHANGE (1 << 3)
 #define XDF_IGNORE_WHITESPACE_AT_EOL (1 << 4)
-#define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | XDF_IGNORE_WHITESPACE_CHANGE | XDF_IGNORE_WHITESPACE_AT_EOL)
+#define XDF_WHITESPACE_FLAGS \
+	(XDF_IGNORE_WHITESPACE | \
+	 XDF_IGNORE_WHITESPACE_CHANGE | \
+	 XDF_IGNORE_WHITESPACE_AT_EOL)
+#define XDF_INEXACT_MATCH XDF_WHITESPACE_FLAGS
 
 #define XDF_PATIENCE_DIFF (1 << 5)
 #define XDF_HISTOGRAM_DIFF (1 << 6)
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index 0de084e..aa6de74 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -176,7 +176,7 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 
 	if (s1 == s2 && !memcmp(l1, l2, s1))
 		return 1;
-	if (!(flags & XDF_WHITESPACE_FLAGS))
+	if (!(flags & XDF_INEXACT_MATCH))
 		return 0;
 
 	i1 = 0;
@@ -281,7 +281,7 @@ unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
 	unsigned long ha = 5381;
 	char const *ptr = *data;
 
-	if (flags & XDF_WHITESPACE_FLAGS)
+	if (flags & XDF_INEXACT_MATCH)
 		return xdl_hash_record_with_whitespace(data, top, flags);
 
 	for (; ptr < top && *ptr != '\n'; ptr++) {

xdiff/xdiff.h, xdiff/xutils.c

diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 48793f9..5a01a0e 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -36,10 +36,11 @@ extern "C" {
 	(XDF_IGNORE_WHITESPACE | \
 	 XDF_IGNORE_WHITESPACE_CHANGE | \
 	 XDF_IGNORE_WHITESPACE_AT_EOL)
-#define XDF_INEXACT_MATCH XDF_WHITESPACE_FLAGS
+#define XDF_IGNORE_CASE (1 << 7)
+#define XDF_INEXACT_MATCH (XDF_WHITESPACE_FLAGS | XDF_IGNORE_CASE)
 
-#define XDF_PATIENCE_DIFF (1 << 5)
-#define XDF_HISTOGRAM_DIFF (1 << 6)
+#define XDF_PATIENCE_DIFF (1 << 8)
+#define XDF_HISTOGRAM_DIFF (1 << 9)
 #define XDF_DIFF_ALGORITHM_MASK (XDF_PATIENCE_DIFF | XDF_HISTOGRAM_DIFF)
 #define XDF_DIFF_ALG(x) ((x) & XDF_DIFF_ALGORITHM_MASK)
 
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index aa6de74..925f1d0 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -170,6 +170,19 @@ long xdl_guess_lines(mmfile_t *mf, long sample) {
 	return nl + 1;
 }
 
+static inline int match_a_byte(char ch1, char ch2, long flags)
+{
+	if (ch1 == ch2)
+		return 1;
+	if (!(flags & XDF_IGNORE_CASE) || ((ch1 | ch2) & 0x80))
+		return 0;
+	if (isupper(ch1))
+		ch1 = tolower(ch1);
+	if (isupper(ch2))
+		ch2 = tolower(ch2);
+	return (ch1 == ch2);
+}
+
 int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 {
 	int i1, i2;
@@ -192,7 +205,7 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 	if (flags & XDF_IGNORE_WHITESPACE) {
 		goto skip_ws;
 		while (i1 < s1 && i2 < s2) {
-			if (l1[i1++] != l2[i2++])
+			if (!match_a_byte(l1[i1++], l2[i2++], flags))
 				return 0;
 		skip_ws:
 			while (i1 < s1 && XDL_ISSPACE(l1[i1]))
@@ -210,15 +223,28 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 					i2++;
 				continue;
 			}
-			if (l1[i1++] != l2[i2++])
+			if (!match_a_byte(l1[i1++], l2[i2++], flags))
 				return 0;
 		}
-	} else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL) {
-		while (i1 < s1 && i2 < s2 && l1[i1++] == l2[i2++])
+	} else {
+		/*
+		 * Either XDF_IGNORE_WHITESPACE_AT_EOL is set, or
+		 * no whitespace is ignored, but INEXACT_MATCH is
+		 * in effect for other reasons.
+		 */
+		while (i1 < s1 && i2 < s2 &&
+		       match_a_byte(l1[i1++], l2[i2++], flags))
 			; /* keep going */
 	}
 
 	/*
+	 * If we are not ignoring any whitespace, we must have consumed
+	 * everything for the lines to match.
+	 */
+	if (!(flags & XDF_WHITESPACE_FLAGS))
+		return i1 == s1 && i2 == s2;
+
+	/*
 	 * After running out of one side, the remaining side must have
 	 * nothing but whitespace for the lines to match.  Note that
 	 * ignore-whitespace-at-eol case may break out of the loop
@@ -238,6 +264,14 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 	return 1;
 }
 
+static inline unsigned long hash_a_byte(const char ch_, long flags)
+{
+	unsigned long ch = ch_ & 0xFF;
+	if ((flags & XDF_IGNORE_CASE) && !(ch & 0x80) && isupper(ch))
+		ch = tolower(ch);
+	return ch;
+}
+
 static unsigned long xdl_hash_record_with_whitespace(char const **data,
 		char const *top, long flags) {
 	unsigned long ha = 5381;
@@ -256,20 +290,20 @@ static unsigned long xdl_hash_record_with_whitespace(char const **data,
 			else if (flags & XDF_IGNORE_WHITESPACE_CHANGE
 				 && !at_eol) {
 				ha += (ha << 5);
-				ha ^= (unsigned long) ' ';
+				ha ^= hash_a_byte(' ', flags);
 			}
 			else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL
 				 && !at_eol) {
 				while (ptr2 != ptr + 1) {
 					ha += (ha << 5);
-					ha ^= (unsigned long) *ptr2;
+					ha ^= hash_a_byte(*ptr2, flags);
 					ptr2++;
 				}
 			}
 			continue;
 		}
 		ha += (ha << 5);
-		ha ^= (unsigned long) *ptr;
+		ha ^= hash_a_byte(*ptr, flags);
 	}
 	*data = ptr < top ? ptr + 1: ptr;
 
@@ -286,7 +320,7 @@ unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
 
 	for (; ptr < top && *ptr != '\n'; ptr++) {
 		ha += (ha << 5);
-		ha ^= (unsigned long) *ptr;
+		ha ^= hash_a_byte(*ptr, flags);
 	}
 	*data = ptr < top ? ptr + 1: ptr;
 

Documentation/diff-options.txt, diff.c, t/lib-diff-alternative.sh, t/t4033-diff-patience.sh, t/t4050-diff-histogram.sh

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 9f7cba2..791e07f 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -404,6 +404,10 @@ endif::git-format-patch[]
 	differences even if one line has whitespace where the other
 	line has none.
 
+--ignore-case::
+	Ignore changes in case only; only ASCII alphabet is supported for
+	now.
+
 --inter-hunk-context=<lines>::
 	Show the context between diff hunks, up to the specified number
 	of lines, thereby fusing hunks that are close to each other.
diff --git a/diff.c b/diff.c
index 87b2ec1..d7604b7 100644
--- a/diff.c
+++ b/diff.c
@@ -3399,6 +3399,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_XDL_SET(options, IGNORE_WHITESPACE_CHANGE);
 	else if (!strcmp(arg, "--ignore-space-at-eol"))
 		DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
+	else if (!strcmp(arg, "--ignore-case"))
+		DIFF_XDL_SET(options, IGNORE_CASE);
 	else if (!strcmp(arg, "--patience"))
 		options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
 	else if (!strcmp(arg, "--histogram"))
diff --git a/t/lib-diff-alternative.sh b/t/lib-diff-alternative.sh
index 75ffd91..45c665e 100644
--- a/t/lib-diff-alternative.sh
+++ b/t/lib-diff-alternative.sh
@@ -104,8 +104,9 @@ EOF
 
 	STRATEGY=$1
 
+	cmd='git diff --no-index'
 	test_expect_success "$STRATEGY diff" '
-		test_must_fail git diff --no-index "--$STRATEGY" file1 file2 > output &&
+		test_must_fail $cmd ${STRATEGY:+"--$STRATEGY"} file1 file2 >output &&
 		test_cmp expect output
 	'
 
@@ -157,9 +158,49 @@ EOF
 
 	STRATEGY=$1
 
+	cmd='git diff --no-index'
 	test_expect_success 'completely different files' '
-		test_must_fail git diff --no-index "--$STRATEGY" uniq1 uniq2 > output &&
+
+		test_must_fail $cmd  ${STRATEGY:+"--$STRATEGY"} uniq1 uniq2 >output &&
 		test_cmp expect output
 	'
 }
 
+test_diff_ignore () {
+
+	STRATEGY=$1
+
+	echo "A quick brown fox" >test.0
+	echo "A  quick brown fox" >test-b
+	echo " A quick brownfox" >test-w
+	echo "A quick brown fox " >test--ignore-space-at-eol
+	echo "A Quick Brown Fox" >test--ignore-case
+	echo "A Quick  Brown Fox" >test--ignore-case-b
+	echo "A quick brown fox jumps" >test
+	cases="-b -w --ignore-space-at-eol --ignore-case"
+
+	if test -z "$STRATEGY"
+	then
+		label=baseline
+	else
+		label=$STRATEGY
+	fi
+
+	cmd="git diff --no-index ${STRATEGY:+--$STRATEGY}"
+
+	test_expect_success "$label diff" '
+		test_must_fail $cmd test.0 test
+	'
+	for case in $cases
+	do
+		test_expect_success "$label diff $case" '
+			$cmd $case test.0 test$case &&
+			test_must_fail $cmd test.0 test
+		'
+	done
+
+	test_expect_success "$label diff -b --ignore-case" '
+		$cmd -b --ignore-case test.0 test--ignore-case-b
+	'
+
+}
diff --git a/t/t4033-diff-patience.sh b/t/t4033-diff-patience.sh
index 3c9932e..c7f8c6c 100755
--- a/t/t4033-diff-patience.sh
+++ b/t/t4033-diff-patience.sh
@@ -5,8 +5,14 @@ test_description='patience diff algorithm'
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-diff-alternative.sh
 
+# baseline
+test_diff_unique ""
+test_diff_ignore ""
+
 test_diff_frobnitz "patience"
 
 test_diff_unique "patience"
 
+test_diff_ignore "patience"
+
 test_done
diff --git a/t/t4050-diff-histogram.sh b/t/t4050-diff-histogram.sh
index fd3e86a..98c6686 100755
--- a/t/t4050-diff-histogram.sh
+++ b/t/t4050-diff-histogram.sh
@@ -9,4 +9,6 @@ test_diff_frobnitz "histogram"
 
 test_diff_unique "histogram"
 
+test_diff_ignore "histogram"
+
 test_done

Documentation/diff-options.txt, diff.c, revision.c, t/lib-diff-alternative.sh

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 791e07f..9ed78c9 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -404,6 +404,7 @@ endif::git-format-patch[]
 	differences even if one line has whitespace where the other
 	line has none.
 
+-i::
 --ignore-case::
 	Ignore changes in case only; only ASCII alphabet is supported for
 	now.
diff --git a/diff.c b/diff.c
index d7604b7..9d1584e 100644
--- a/diff.c
+++ b/diff.c
@@ -3399,7 +3399,7 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_XDL_SET(options, IGNORE_WHITESPACE_CHANGE);
 	else if (!strcmp(arg, "--ignore-space-at-eol"))
 		DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
-	else if (!strcmp(arg, "--ignore-case"))
+	else if (!strcmp(arg, "--ignore-case") || !strcmp(arg, "-i"))
 		DIFF_XDL_SET(options, IGNORE_CASE);
 	else if (!strcmp(arg, "--patience"))
 		options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
diff --git a/revision.c b/revision.c
index 8764dde..f1a1354 100644
--- a/revision.c
+++ b/revision.c
@@ -13,6 +13,7 @@
 #include "decorate.h"
 #include "log-tree.h"
 #include "string-list.h"
+#include "xdiff-interface.h"
 
 volatile show_early_output_fn_t show_early_output;
 
@@ -1557,7 +1558,10 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		return argcount;
 	} else if (!strcmp(arg, "--extended-regexp") || !strcmp(arg, "-E")) {
 		revs->grep_filter.regflags |= REG_EXTENDED;
-	} else if (!strcmp(arg, "--regexp-ignore-case") || !strcmp(arg, "-i")) {
+	} else if (!strcmp(arg, "-i")) {
+		DIFF_XDL_SET(&revs->diffopt, IGNORE_CASE);
+		revs->grep_filter.regflags |= REG_ICASE;
+	} else if (!strcmp(arg, "--regexp-ignore-case")) {
 		revs->grep_filter.regflags |= REG_ICASE;
 	} else if (!strcmp(arg, "--fixed-strings") || !strcmp(arg, "-F")) {
 		revs->grep_filter.fixed = 1;
diff --git a/t/lib-diff-alternative.sh b/t/lib-diff-alternative.sh
index 45c665e..81609f8 100644
--- a/t/lib-diff-alternative.sh
+++ b/t/lib-diff-alternative.sh
@@ -175,9 +175,10 @@ test_diff_ignore () {
 	echo " A quick brownfox" >test-w
 	echo "A quick brown fox " >test--ignore-space-at-eol
 	echo "A Quick Brown Fox" >test--ignore-case
+	echo "A Quick Brown FoX" >test-i
 	echo "A Quick  Brown Fox" >test--ignore-case-b
 	echo "A quick brown fox jumps" >test
-	cases="-b -w --ignore-space-at-eol --ignore-case"
+	cases="-b -w --ignore-space-at-eol --ignore-case -i"
 
 	if test -z "$STRATEGY"
 	then

diff.h, diffcore-pickaxe.c, revision.c

diff --git a/diff.h b/diff.h
index 7af5f1e..182cb0e 100644
--- a/diff.h
+++ b/diff.h
@@ -82,6 +82,7 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_OPT_OVERRIDE_SUBMODULE_CONFIG (1 << 27)
 #define DIFF_OPT_DIRSTAT_BY_LINE     (1 << 28)
 #define DIFF_OPT_FUNCCONTEXT         (1 << 29)
+#define DIFF_OPT_PICKAXE_IGNORE_CASE (1 << 30)
 
 #define DIFF_OPT_TST(opts, flag)    ((opts)->flags & DIFF_OPT_##flag)
 #define DIFF_OPT_SET(opts, flag)    ((opts)->flags |= DIFF_OPT_##flag)
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index 380a837..8ffb741 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -138,8 +138,12 @@ static void diffcore_pickaxe_grep(struct diff_options *o)
 {
 	int err;
 	regex_t regex;
+	int cflags = REG_EXTENDED | REG_NEWLINE;
 
-	err = regcomp(&regex, o->pickaxe, REG_EXTENDED | REG_NEWLINE);
+	if (DIFF_OPT_TST(o, PICKAXE_IGNORE_CASE))
+		cflags |= REG_ICASE;
+
+	err = regcomp(&regex, o->pickaxe, cflags);
 	if (err) {
 		char errbuf[1024];
 		regerror(err, &regex, errbuf, 1024);
diff --git a/revision.c b/revision.c
index 819ff01..b3554ed 100644
--- a/revision.c
+++ b/revision.c
@@ -1582,6 +1582,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->grep_filter.regflags |= REG_EXTENDED;
 	} else if (!strcmp(arg, "--regexp-ignore-case") || !strcmp(arg, "-i")) {
 		revs->grep_filter.regflags |= REG_ICASE;
+		DIFF_OPT_SET(&revs->diffopt, PICKAXE_IGNORE_CASE);
 	} else if (!strcmp(arg, "--fixed-strings") || !strcmp(arg, "-F")) {
 		revs->grep_filter.fixed = 1;
 	} else if (!strcmp(arg, "--all-match")) {