[RFC PATCH 6/7] rebase -i: Prepare for squash in terms of do_pick --amend

[Fabian Ruch <bafain@gmail.com>]

Rewrite `squash` and `fixup` handling in `do_next` using the atomic
sequence

    pick_one
    commit

in order to test the correctness of a single `do_squash` or parametrized
`do_pick` and make the subsequent patch reimplementing `squash` in terms
of such a single function more readable.

Might be squashed into the subsequent commit.

Signed-off-by: Fabian Ruch <bafain@gmail.com>
---
 git-rebase--interactive.sh | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index e4992dc..ada520d 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -613,15 +613,15 @@ do_next () {
 		author_script_content=$(get_author_ident_from_commit HEAD)
 		echo "$author_script_content" > "$author_script"
 		eval "$author_script_content"
-		if ! pick_one -n $sha1
-		then
-			git rev-parse --verify HEAD >"$amend"
-			die_failed_squash $sha1 "$rest"
-		fi
 		case "$(peek_next_command)" in
 		squash|s|fixup|f)
 			# This is an intermediate commit; its message will only be
 			# used in case of trouble.  So use the long version:
+			if ! pick_one -n $sha1
+			then
+				git rev-parse --verify HEAD >"$amend"
+				die_failed_squash $sha1 "Could not apply $sha1... $rest"
+			fi
 			do_with_author output git commit --amend --no-verify -F "$squash_msg" \
 				${gpg_sign_opt:+"$gpg_sign_opt"} ||
 				die_failed_squash $sha1 "$rest"
@@ -630,12 +630,22 @@ do_next () {
 			# This is the final command of this squash/fixup group
 			if test -f "$fixup_msg"
 			then
+				if ! pick_one -n $sha1
+				then
+					git rev-parse --verify HEAD >"$amend"
+					die_failed_squash $sha1 "Could not apply $sha1... $rest"
+				fi
 				do_with_author git commit --amend --no-verify -F "$fixup_msg" \
 					${gpg_sign_opt:+"$gpg_sign_opt"} ||
 					die_failed_squash $sha1 "$rest"
 			else
 				cp "$squash_msg" "$GIT_DIR"/SQUASH_MSG || exit
 				rm -f "$GIT_DIR"/MERGE_MSG
+				if ! pick_one -n $sha1
+				then
+					git rev-parse --verify HEAD >"$amend"
+					die_failed_squash $sha1 "Could not apply $sha1... $rest"
+				fi
 				do_with_author git commit --amend --no-verify -F "$GIT_DIR"/SQUASH_MSG -e \
 					${gpg_sign_opt:+"$gpg_sign_opt"} ||
 					die_failed_squash $sha1 "$rest"
-- 
2.0.0