rebase: turn on progress option by default for format-patch

Pass the "--progress" option to format-patch when the standard error
stream is connected to the terminal and "--quiet" is not given.

Signed-off-by: Kevin Willford <kewillf@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase--am.sh

@@ -53,6 +53,7 @@ else
 
 	git format-patch -k --stdout --full-index --cherry-pick --right-only \
 		--src-prefix=a/ --dst-prefix=b/ --no-renames --no-cover-letter \
+		$git_format_patch_opt \
 		"$revisions" ${restrict_revision+^$restrict_revision} \
 		>"$GIT_DIR/rebased-patches"
 	ret=$?

git-rebase.sh

@@ -73,6 +73,7 @@ test "$(git config --bool rebase.stat)" = true && diffstat=t
 autostash="$(git config --bool rebase.autostash || echo false)"
 fork_point=auto
 git_am_opt=
+git_format_patch_opt=
 rebase_root=
 force_rebase=
 allow_rerere_autoupdate=
@@ -444,6 +445,11 @@ else
 	state_dir="$apply_dir"
 fi
 
+if test -t 2 && test -z "$GIT_QUIET"
+then
+	git_format_patch_opt="$git_format_patch_opt --progress"
+fi
+
 if test -z "$rebase_root"
 then
 	case "$#" in