git-blame -w: ignore whitespace

When refactoring code to split one iteration of a too deeply
nested loop into a separate function, it inevitably makes the
indentation levels shallower (that's the sole point of such a
refactoring).  With "git blame -w", you can ignore such
re-indentation and pass blame for such moved lines to the
parent.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-blame.txt

@@ -8,7 +8,7 @@ git-blame - Show what revision and author last modified each line of a file
 SYNOPSIS
 --------
 [verse]
-'git-blame' [-c] [-b] [--root] [-s] [-l] [-t] [-f] [-n] [-p] [--incremental] [-L n,m]
+'git-blame' [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-w] [--incremental] [-L n,m]
             [-S <revs-file>] [-M] [-C] [-C] [--since=<date>]
             [<rev> | --contents <file>] [--] <file>
 
@@ -63,6 +63,11 @@ include::blame-options.txt[]
 -s::
 	Suppress author name and timestamp from the output.
 
+-w::
+	Ignore whitespace when comparing parent's version and
+	child's to find where the lines came from.
+
+
 THE PORCELAIN FORMAT
 --------------------
 

builtin-blame.c

@@ -20,7 +20,7 @@
 #include "mailmap.h"
 
 static char blame_usage[] =
-"git-blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-L n,m] [-S <revs-file>] [-M] [-C] [-C] [--contents <filename>] [--incremental] [commit] [--] file\n"
+"git-blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-w] [-L n,m] [-S <revs-file>] [-M] [-C] [-C] [--contents <filename>] [--incremental] [commit] [--] file\n"
 "  -c                  Use the same output mode as git-annotate (Default: off)\n"
 "  -b                  Show blank SHA-1 for boundary commits (Default: off)\n"
 "  -l                  Show long commit SHA1 (Default: off)\n"
@@ -30,6 +30,7 @@ static char blame_usage[] =
 "  -n, --show-number   Show original linenumber (Default: off)\n"
 "  -s                  Suppress author name and timestamp (Default: off)\n"
 "  -p, --porcelain     Show in a format designed for machine consumption\n"
+"  -w                  Ignore whitespace differences\n"
 "  -L n,m              Process only line range n,m, counting from 1\n"
 "  -M, -C              Find line movements within and across files\n"
 "  --incremental       Show blame entries as we find them, incrementally\n"
@@ -45,6 +46,7 @@ static int show_root;
 static int blank_boundary;
 static int incremental;
 static int cmd_is_annotate;
+static int xdl_opts = XDF_NEED_MINIMAL;
 static struct path_list mailmap;
 
 #ifndef DEBUG
@@ -515,7 +517,7 @@ static struct patch *compare_buffer(mmfile_t *file_p, mmfile_t *file_o,
 	xdemitconf_t xecfg;
 	xdemitcb_t ecb;
 
-	xpp.flags = XDF_NEED_MINIMAL;
+	xpp.flags = xdl_opts;
 	xecfg.ctxlen = context;
 	xecfg.flags = 0;
 	ecb.outf = xdiff_outf;
@@ -2159,6 +2161,8 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 			output_option |= OUTPUT_LONG_OBJECT_NAME;
 		else if (!strcmp("-s", arg))
 			output_option |= OUTPUT_NO_AUTHOR;
+		else if (!strcmp("-w", arg))
+			xdl_opts |= XDF_IGNORE_WHITESPACE;
 		else if (!strcmp("-S", arg) && ++i < argc)
 			revs_file = argv[i];
 		else if (!prefixcmp(arg, "-M")) {