refspec: add support for negative refspecs

Both fetch and push support pattern refspecs which allow fetching or
pushing references that match a specific pattern. Because these patterns
are globs, they have somewhat limited ability to express more complex
situations.

For example, suppose you wish to fetch all branches from a remote except
for a specific one. To allow this, you must setup a set of refspecs
which match only the branches you want. Because refspecs are either
explicit name matches, or simple globs, many patterns cannot be
expressed.

Add support for a new type of refspec, referred to as "negative"
refspecs. These are prefixed with a '^' and mean "exclude any ref
matching this refspec". They can only have one "side" which always
refers to the source. During a fetch, this refers to the name of the ref
on the remote. During a push, this refers to the name of the ref on the
local side.

With negative refspecs, users can express more complex patterns. For
example:

 git fetch origin refs/heads/*:refs/remotes/origin/* ^refs/heads/dontwant

will fetch all branches on origin into remotes/origin, but will exclude
fetching the branch named dontwant.

Refspecs today are commutative, meaning that order doesn't expressly
matter. Rather than forcing an implied order, negative refspecs will
always be applied last. That is, in order to match, a ref must match at
least one positive refspec, and match none of the negative refspecs.
This is similar to how negative pathspecs work.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 189 insertions, 0 deletions

diff --git a/t/t5582-fetch-negative-refspec.sh b/t/t5582-fetch-negative-refspec.sh
new file mode 100755
index 0000000..8c61e28
--- /dev/null
+++ b/t/t5582-fetch-negative-refspec.sh
@@ -0,0 +1,189 @@
+#!/bin/sh
+# Copyright (c) 2020, Jacob Keller.
+
+test_description='"git fetch" with negative refspecs.
+
+'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	echo >file original &&
+	git add file &&
+	git commit -a -m original
+'
+
+test_expect_success "clone and setup child repos" '
+	git clone . one &&
+	(
+		cd one &&
+		echo >file updated by one &&
+		git commit -a -m "updated by one" &&
+		git switch -c alternate &&
+		echo >file updated again by one &&
+		git commit -a -m "updated by one again" &&
+		git switch master
+	) &&
+	git clone . two &&
+	(
+		cd two &&
+		git config branch.master.remote one &&
+		git config remote.one.url ../one/.git/ &&
+		git config remote.one.fetch +refs/heads/*:refs/remotes/one/* &&
+		git config --add remote.one.fetch ^refs/heads/alternate
+	) &&
+	git clone . three
+'
+
+test_expect_success "fetch one" '
+	echo >file updated by origin &&
+	git commit -a -m "updated by origin" &&
+	(
+		cd two &&
+		test_must_fail git rev-parse --verify refs/remotes/one/alternate &&
+		git fetch one &&
+		test_must_fail git rev-parse --verify refs/remotes/one/alternate &&
+		git rev-parse --verify refs/remotes/one/master &&
+		mine=$(git rev-parse refs/remotes/one/master) &&
+		his=$(cd ../one && git rev-parse refs/heads/master) &&
+		test "z$mine" = "z$his"
+	)
+'
+
+test_expect_success "fetch with negative refspec on commandline" '
+	echo >file updated by origin again &&
+	git commit -a -m "updated by origin again" &&
+	(
+		cd three &&
+		alternate_in_one=$(cd ../one && git rev-parse refs/heads/alternate) &&
+		echo $alternate_in_one >expect &&
+		git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^refs/heads/master &&
+		cut -f -1 .git/FETCH_HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch with negative sha1 refspec fails" '
+	echo >file updated by origin yet again &&
+	git commit -a -m "updated by origin yet again" &&
+	(
+		cd three &&
+		master_in_one=$(cd ../one && git rev-parse refs/heads/master) &&
+		test_must_fail git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^$master_in_one
+	)
+'
+
+test_expect_success "fetch with negative pattern refspec" '
+	echo >file updated by origin once more &&
+	git commit -a -m "updated by origin once more" &&
+	(
+		cd three &&
+		alternate_in_one=$(cd ../one && git rev-parse refs/heads/alternate) &&
+		echo $alternate_in_one >expect &&
+		git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^refs/heads/m* &&
+		cut -f -1 .git/FETCH_HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch with negative pattern refspec does not expand prefix" '
+	echo >file updated by origin another time &&
+	git commit -a -m "updated by origin another time" &&
+	(
+		cd three &&
+		alternate_in_one=$(cd ../one && git rev-parse refs/heads/alternate) &&
+		master_in_one=$(cd ../one && git rev-parse refs/heads/master) &&
+		echo $alternate_in_one >expect &&
+		echo $master_in_one >>expect &&
+		git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^master &&
+		cut -f -1 .git/FETCH_HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch with negative refspec avoids duplicate conflict" '
+	cd "$D" &&
+	(
+		cd one &&
+		git branch dups/a &&
+		git branch dups/b &&
+		git branch dups/c &&
+		git branch other/a &&
+		git rev-parse --verify refs/heads/other/a >../expect &&
+		git rev-parse --verify refs/heads/dups/b >>../expect &&
+		git rev-parse --verify refs/heads/dups/c >>../expect
+	) &&
+	(
+		cd three &&
+		git fetch ../one/.git ^refs/heads/dups/a refs/heads/dups/*:refs/dups/* refs/heads/other/a:refs/dups/a &&
+		git rev-parse --verify refs/dups/a >../actual &&
+		git rev-parse --verify refs/dups/b >>../actual &&
+		git rev-parse --verify refs/dups/c >>../actual
+	) &&
+	test_cmp expect actual
+'
+
+test_expect_success "push --prune with negative refspec" '
+	(
+		cd two &&
+		git branch prune/a &&
+		git branch prune/b &&
+		git branch prune/c &&
+		git push ../three refs/heads/prune/* &&
+		git branch -d prune/a &&
+		git branch -d prune/b &&
+		git push --prune ../three refs/heads/prune/* ^refs/heads/prune/b
+	) &&
+	(
+		cd three &&
+		test_write_lines b c >expect &&
+		git for-each-ref --format="%(refname:lstrip=3)" refs/heads/prune/ >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "push --prune with negative refspec apply to the destination" '
+	(
+		cd two &&
+		git branch ours/a &&
+		git branch ours/b &&
+		git branch ours/c &&
+		git push ../three refs/heads/ours/*:refs/heads/theirs/* &&
+		git branch -d ours/a &&
+		git branch -d ours/b &&
+		git push --prune ../three refs/heads/ours/*:refs/heads/theirs/* ^refs/heads/theirs/b
+	) &&
+	(
+		cd three &&
+		test_write_lines b c >expect &&
+		git for-each-ref --format="%(refname:lstrip=3)" refs/heads/theirs/ >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch --prune with negative refspec" '
+	(
+		cd two &&
+		git branch fetch/a &&
+		git branch fetch/b &&
+		git branch fetch/c
+	) &&
+	(
+		cd three &&
+		git fetch ../two/.git refs/heads/fetch/*:refs/heads/copied/*
+	) &&
+	(
+		cd two &&
+		git branch -d fetch/a &&
+		git branch -d fetch/b
+	) &&
+	(
+		cd three &&
+		test_write_lines b c >expect &&
+		git fetch -v ../two/.git --prune refs/heads/fetch/*:refs/heads/copied/* ^refs/heads/fetch/b &&
+		git for-each-ref --format="%(refname:lstrip=3)" refs/heads/copied/ >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_done