sha1_file.c: rename to use dash in file name

This is more consistent with the project style. The majority of Git's
source files use dashes in preference to underscores in their file names.

Signed-off-by: Stefan Beller <sbeller@google.com>

Documentation/technical/api-object-access.txt

@@ -1,7 +1,7 @@
 object access API
 =================
 
-Talk about <sha1_file.c> and <object.h> family, things like
+Talk about <sha1-file.c> and <object.h> family, things like
 
 * read_sha1_file()
 * read_object_with_reference()

Makefile

@@ -900,7 +900,7 @@ LIB_OBJS += server-info.o
 LIB_OBJS += setup.o
 LIB_OBJS += sha1-array.o
 LIB_OBJS += sha1-lookup.o
-LIB_OBJS += sha1_file.o
+LIB_OBJS += sha1-file.o
 LIB_OBJS += sha1-name.o
 LIB_OBJS += shallow.o
 LIB_OBJS += sideband.o

builtin/index-pack.c

@@ -1593,7 +1593,7 @@ static void read_idx_option(struct pack_idx_option *opts, const char *pack_name)
 	/*
 	 * Get rid of the idx file as we do not need it anymore.
 	 * NEEDSWORK: extract this bit from free_pack_by_name() in
-	 * sha1_file.c, perhaps?  It shouldn't matter very much as we
+	 * sha1-file.c, perhaps?  It shouldn't matter very much as we
 	 * know we haven't installed this pack (hence we never have
 	 * read anything from it).
 	 */