cherry-pick: use better advice message

"git cherry-pick", upon seeing a conflict, says:

hint: after resolving the conflicts, mark the corrected paths
hint: with 'git add <paths>' or 'git rm <paths>'
hint: and commit the result with 'git commit'

as if running "git commit" to conclude the resolution of
this single step were the end of the story.  This stems from
the fact that the command originally was to pick a single
commit and not a range of commits, and the message was
written back then and has not been adjusted.

When picking a range of commits and the command stops with a
conflict in the middle of the range, however, after
resolving the conflict and (optionally) recording the result
with "git commit", the user has to run "git cherry-pick
--continue" to have the rest of the range dealt with,
"--skip" to drop the current commit, or "--abort" to discard
the series.

Suggest use of "git cherry-pick --continue/--skip/--abort"
so that the message also covers the case where a range of
commits are being picked.

Similarly, this optimization can be applied to git revert,
suggest use of "git revert --continue/--skip/--abort" so
that the message also covers the case where a range of
commits are being reverted.

It is worth mentioning that now we use advice() to print
the content of GIT_CHERRY_PICK_HELP in print_advice(), each
line of output will start with "hint: ".

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Hariom Verma <hariom18599@gmail.com>
Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sequencer.c

@@ -403,7 +403,7 @@ static void print_advice(struct repository *r, int show_hint,
 	char *msg = getenv("GIT_CHERRY_PICK_HELP");
 
 	if (msg) {
-		fprintf(stderr, "%s\n", msg);
+		advise("%s\n", msg);
 		/*
 		 * A conflict has occurred but the porcelain
 		 * (typically rebase --interactive) wants to take care
@@ -418,10 +418,22 @@ static void print_advice(struct repository *r, int show_hint,
 		if (opts->no_commit)
 			advise(_("after resolving the conflicts, mark the corrected paths\n"
 				 "with 'git add <paths>' or 'git rm <paths>'"));
+		else if (opts->action == REPLAY_PICK)
+			advise(_("After resolving the conflicts, mark them with\n"
+				 "\"git add/rm <pathspec>\", then run\n"
+				 "\"git cherry-pick --continue\".\n"
+				 "You can instead skip this commit with \"git cherry-pick --skip\".\n"
+				 "To abort and get back to the state before \"git cherry-pick\",\n"
+				 "run \"git cherry-pick --abort\"."));
+		else if (opts->action == REPLAY_REVERT)
+			advise(_("After resolving the conflicts, mark them with\n"
+				 "\"git add/rm <pathspec>\", then run\n"
+				 "\"git revert --continue\".\n"
+				 "You can instead skip this commit with \"git revert --skip\".\n"
+				 "To abort and get back to the state before \"git revert\",\n"
+				 "run \"git revert --abort\"."));
 		else
-			advise(_("after resolving the conflicts, mark the corrected paths\n"
-				 "with 'git add <paths>' or 'git rm <paths>'\n"
-				 "and commit the result with 'git commit'"));
+			BUG("unexpected pick action in print_advice()");
 	}
 }
 

t/t3501-revert-cherry-pick.sh

@@ -158,4 +158,20 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
 	grep -q "^modified$" renamed
 '
 
+test_expect_success 'advice from failed revert' '
+	test_commit --no-tag "add dream" dream dream &&
+	dream_oid=$(git rev-parse --short HEAD) &&
+	cat <<-EOF >expected &&
+	error: could not revert $dream_oid... add dream
+	hint: After resolving the conflicts, mark them with
+	hint: "git add/rm <pathspec>", then run
+	hint: "git revert --continue".
+	hint: You can instead skip this commit with "git revert --skip".
+	hint: To abort and get back to the state before "git revert",
+	hint: run "git revert --abort".
+	EOF
+	test_commit --append --no-tag "double-add dream" dream dream &&
+	test_must_fail git revert HEAD^ 2>actual &&
+	test_cmp expected actual
+'
 test_done

t/t3507-cherry-pick-conflict.sh

@@ -47,20 +47,23 @@ test_expect_success 'failed cherry-pick does not advance HEAD' '
 	test "$head" = "$newhead"
 '
 
-test_expect_success 'advice from failed cherry-pick' "
+test_expect_success 'advice from failed cherry-pick' '
 	pristine_detach initial &&
 
-	picked=\$(git rev-parse --short picked) &&
+	picked=$(git rev-parse --short picked) &&
 	cat <<-EOF >expected &&
-	error: could not apply \$picked... picked
-	hint: after resolving the conflicts, mark the corrected paths
-	hint: with 'git add <paths>' or 'git rm <paths>'
-	hint: and commit the result with 'git commit'
+	error: could not apply $picked... picked
+	hint: After resolving the conflicts, mark them with
+	hint: "git add/rm <pathspec>", then run
+	hint: "git cherry-pick --continue".
+	hint: You can instead skip this commit with "git cherry-pick --skip".
+	hint: To abort and get back to the state before "git cherry-pick",
+	hint: run "git cherry-pick --abort".
 	EOF
 	test_must_fail git cherry-pick picked 2>actual &&
 
 	test_cmp expected actual
-"
+'
 
 test_expect_success 'advice from failed cherry-pick --no-commit' "
 	pristine_detach initial &&