reset: support the --pathspec-from-file option

Decisions taken for simplicity:
1) For now, `--pathspec-from-file` is declared incompatible with
   `--patch`, even when <file> is not `stdin`. Such use case it not
   really expected. Also, it is harder to support in `git commit`, so
   I decided to make it incompatible in all places.
2) It is not allowed to pass pathspec in both args and file.

Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7107-reset-pathspec-file.sh

@@ -0,0 +1,155 @@
+#!/bin/sh
+
+test_description='reset --pathspec-from-file'
+
+. ./test-lib.sh
+
+test_tick
+
+test_expect_success setup '
+	echo A >fileA.t &&
+	echo B >fileB.t &&
+	echo C >fileC.t &&
+	echo D >fileD.t &&
+	git add . &&
+	git commit --include . -m "Commit" &&
+	git tag checkpoint
+'
+
+restore_checkpoint () {
+	git reset --hard checkpoint
+}
+
+verify_expect () {
+	git status --porcelain -- fileA.t fileB.t fileC.t fileD.t >actual &&
+	test_cmp expect actual
+}
+
+test_expect_success '--pathspec-from-file from stdin' '
+	restore_checkpoint &&
+
+	git rm fileA.t &&
+	echo fileA.t | git reset --pathspec-from-file=- &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	EOF
+	verify_expect
+'
+
+test_expect_success '--pathspec-from-file from file' '
+	restore_checkpoint &&
+
+	git rm fileA.t &&
+	echo fileA.t >list &&
+	git reset --pathspec-from-file=list &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	EOF
+	verify_expect
+'
+
+test_expect_success 'NUL delimiters' '
+	restore_checkpoint &&
+
+	git rm fileA.t fileB.t &&
+	printf "fileA.t\0fileB.t\0" | git reset --pathspec-from-file=- --pathspec-file-nul &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	 D fileB.t
+	EOF
+	verify_expect
+'
+
+test_expect_success 'LF delimiters' '
+	restore_checkpoint &&
+
+	git rm fileA.t fileB.t &&
+	printf "fileA.t\nfileB.t\n" | git reset --pathspec-from-file=- &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	 D fileB.t
+	EOF
+	verify_expect
+'
+
+test_expect_success 'no trailing delimiter' '
+	restore_checkpoint &&
+
+	git rm fileA.t fileB.t &&
+	printf "fileA.t\nfileB.t" | git reset --pathspec-from-file=- &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	 D fileB.t
+	EOF
+	verify_expect
+'
+
+test_expect_success 'CRLF delimiters' '
+	restore_checkpoint &&
+
+	git rm fileA.t fileB.t &&
+	printf "fileA.t\r\nfileB.t\r\n" | git reset --pathspec-from-file=- &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	 D fileB.t
+	EOF
+	verify_expect
+'
+
+test_expect_success 'quotes' '
+	restore_checkpoint &&
+
+	git rm fileA.t &&
+	printf "\"file\\101.t\"" | git reset --pathspec-from-file=- &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	EOF
+	verify_expect
+'
+
+test_expect_success 'quotes not compatible with --pathspec-file-nul' '
+	restore_checkpoint &&
+
+	git rm fileA.t &&
+	printf "\"file\\101.t\"" >list &&
+	# Note: "git reset" has not yet learned to fail on wrong pathspecs
+	git reset --pathspec-from-file=list --pathspec-file-nul &&
+
+	cat >expect <<-\EOF &&
+	 D fileA.t
+	EOF
+	test_must_fail verify_expect
+'
+
+test_expect_success '--pathspec-from-file is not compatible with --soft or --hard' '
+	restore_checkpoint &&
+
+	git rm fileA.t &&
+	echo fileA.t >list &&
+	test_must_fail git reset --soft --pathspec-from-file=list &&
+	test_must_fail git reset --hard --pathspec-from-file=list
+'
+
+test_expect_success 'only touches what was listed' '
+	restore_checkpoint &&
+
+	git rm fileA.t fileB.t fileC.t fileD.t &&
+	printf "fileB.t\nfileC.t\n" | git reset --pathspec-from-file=- &&
+
+	cat >expect <<-\EOF &&
+	D  fileA.t
+	 D fileB.t
+	 D fileC.t
+	D  fileD.t
+	EOF
+	verify_expect
+'
+
+test_done