[PATCH 1/3] diff: move show_interdiff() from its own file to diff-lib

[Eric Sunshine <sunshine@sunshineco.com>]

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>
---

Notes:
    Suggested by Duy[1] and seconded by Junio[2] during review.
    
    [1]: https://lore.kernel.org/git/CACsJy8C8RK6HkfoEYJGZg=sgtJS0WksHD3=7Souw3jYebRo=Sg@mail.gmail.com/
    [2]: https://lore.kernel.org/git/xmqqh8kp4otz.fsf@gitster-ct.c.googlers.com/

 Makefile      |  1 -
 builtin/log.c |  1 -
 diff-lib.c    | 24 ++++++++++++++++++++++++
 diff.h        |  2 ++
 interdiff.c   | 28 ----------------------------
 interdiff.h   |  8 --------
 log-tree.c    |  1 -
 7 files changed, 26 insertions(+), 39 deletions(-)
 delete mode 100644 interdiff.c
 delete mode 100644 interdiff.h

diff --git a/Makefile b/Makefile
index 86e5411f39..cf47141939 100644
--- a/Makefile
+++ b/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
diff --git a/builtin/log.c b/builtin/log.c
index b58f8da09e..ae9380da1b 100644
--- a/builtin/log.c
+++ b/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 --git a/diff-lib.c b/diff-lib.c
index 50521e2093..9bab907412 100644
--- a/diff-lib.c
+++ b/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 --git a/diff.h b/diff.h
index e0c0af6286..308937c94b 100644
--- a/diff.h
+++ b/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
diff --git a/interdiff.c b/interdiff.c
deleted file mode 100644
index c81d680a6c..0000000000
--- a/interdiff.c
+++ /dev/null
@@ -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);
-}
diff --git a/interdiff.h b/interdiff.h
deleted file mode 100644
index 01c730a5c9..0000000000
--- a/interdiff.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef INTERDIFF_H
-#define INTERDIFF_H
-
-struct rev_info;
-
-void show_interdiff(struct rev_info *, int indent);
-
-#endif
diff --git a/log-tree.c b/log-tree.c
index 55a68d0c61..39bb362d5e 100644
--- a/log-tree.c
+++ b/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" };
-- 
2.28.0.618.gf4bc123cb7