blame: add support for --[no-]progress option

Teach the command to show progress output when it takes long time to
produce the first line of output; this option cannot be used with
"--incremental" or "--porcelain" options.

git-annotate inherits the option as well.

Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Edmundo Carmona Antoranz <eantoranz@gmail.com>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/blame-options.txt

@@ -70,6 +70,13 @@ include::line-range-format.txt[]
 	iso format is used. For more information, See the discussion
 	of the --date option at linkgit:git-log[1].
 
+--[no-]progress::
+	Progress status is reported on the standard error stream
+	by default when it is attached to a terminal. This flag
+	enables progress reporting even if not attached to a
+	terminal. Can't use `--progress` together with `--porcelain`
+	or `--incremental`.
+
 -M|<num>|::
 	Detect moved or copied lines within a file. When a commit
 	moves or copies a block of lines (e.g. the original file

Documentation/git-blame.txt

@@ -10,7 +10,8 @@ SYNOPSIS
 [verse]
 'git blame' [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-e] [-p] [-w] [--incremental]
 	    [-L <range>] [-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>]
-	    [--abbrev=<n>] [<rev> | --contents <file> | --reverse <rev>] [--] <file>
+	    [--progress] [--abbrev=<n>] [<rev> | --contents <file> | --reverse <rev>]
+	    [--] <file>
 
 DESCRIPTION
 -----------