diff: move show_interdiff() from its own file to diff-lib

show_interdiff() is a relatively small function and not likely to grow
larger or more complicated. Rather than dedicating an entire source file
to it, relocate it to diff-lib.c which houses other "take two things and
compare them" functions meant to be re-used but not so low-level as to
reside in the core diff implementation.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -883,7 +883,6 @@ LIB_OBJS += hashmap.o
 LIB_OBJS += help.o
 LIB_OBJS += hex.o
 LIB_OBJS += ident.o
-LIB_OBJS += interdiff.o
 LIB_OBJS += json-writer.o
 LIB_OBJS += kwset.o
 LIB_OBJS += levenshtein.o

builtin/log.c

@@ -33,7 +33,6 @@
 #include "commit-slab.h"
 #include "repository.h"
 #include "commit-reach.h"
-#include "interdiff.h"
 #include "range-diff.h"
 
 #define MAIL_DEFAULT_WRAP 72

diff-lib.c

@@ -571,3 +571,27 @@ int index_differs_from(struct repository *r,
 	object_array_clear(&rev.pending);
 	return (rev.diffopt.flags.has_changes != 0);
 }
+
+static struct strbuf *idiff_prefix_cb(struct diff_options *opt, void *data)
+{
+	return data;
+}
+
+void show_interdiff(struct rev_info *rev, int indent)
+{
+	struct diff_options opts;
+	struct strbuf prefix = STRBUF_INIT;
+
+	memcpy(&opts, &rev->diffopt, sizeof(opts));
+	opts.output_format = DIFF_FORMAT_PATCH;
+	opts.output_prefix = idiff_prefix_cb;
+	strbuf_addchars(&prefix, ' ', indent);
+	opts.output_prefix_data = &prefix;
+	diff_setup_done(&opts);
+
+	diff_tree_oid(rev->idiff_oid1, rev->idiff_oid2, "", &opts);
+	diffcore_std(&opts);
+	diff_flush(&opts);
+
+	strbuf_release(&prefix);
+}

diff.h

@@ -600,6 +600,8 @@ int index_differs_from(struct repository *r, const char *def,
 		       const struct diff_flags *flags,
 		       int ita_invisible_in_index);
 
+void show_interdiff(struct rev_info *, int indent);
+
 /*
  * Fill the contents of the filespec "df", respecting any textconv defined by
  * its userdiff driver.  The "driver" parameter must come from a

interdiff.c

@@ -1,28 +0,0 @@
-#include "cache.h"
-#include "commit.h"
-#include "revision.h"
-#include "interdiff.h"
-
-static struct strbuf *idiff_prefix_cb(struct diff_options *opt, void *data)
-{
-	return data;
-}
-
-void show_interdiff(struct rev_info *rev, int indent)
-{
-	struct diff_options opts;
-	struct strbuf prefix = STRBUF_INIT;
-
-	memcpy(&opts, &rev->diffopt, sizeof(opts));
-	opts.output_format = DIFF_FORMAT_PATCH;
-	opts.output_prefix = idiff_prefix_cb;
-	strbuf_addchars(&prefix, ' ', indent);
-	opts.output_prefix_data = &prefix;
-	diff_setup_done(&opts);
-
-	diff_tree_oid(rev->idiff_oid1, rev->idiff_oid2, "", &opts);
-	diffcore_std(&opts);
-	diff_flush(&opts);
-
-	strbuf_release(&prefix);
-}

interdiff.h

@@ -1,8 +0,0 @@
-#ifndef INTERDIFF_H
-#define INTERDIFF_H
-
-struct rev_info;
-
-void show_interdiff(struct rev_info *, int indent);
-
-#endif

log-tree.c

@@ -15,7 +15,6 @@
 #include "sequencer.h"
 #include "line-log.h"
 #include "help.h"
-#include "interdiff.h"
 #include "range-diff.h"
 
 static struct decoration name_decoration = { "object names" };