tests: move combinations no code path tells apart to exhaustive tests

The matrices cross every option of a source type with every other one,
also where the code handling one never looks at the other.  Scenarios
for such combinations are exhaustive, and run in their own tests, which
nix-build tests doesn't build, but nix-build tests -A exhaustive does:

- file and git: drawing inputs combined with rsync's or Git's options,
  since drawing inputs happens after delivery.
- flake: materialize combined with how the flake gets there, except for
  flakes in Git work trees and in subdirectories, since materializing
  copies what got delivered.
- flake-input: materialize for inputs other than dep.
- deploy: /etc/nixos/flake.nix combined with deploying a flake, since it
  only matters without one.
- edge-cases: generated flakes where only delivery matters, and remote
  targets where drawing inputs alone matters, which happens on the target
  alike for every kind of target.

That's 181 of 707 scenarios.

1 files changed, 17 insertions, 13 deletions

diff --git a/README.md b/README.md
index d8f0346..1b7e29e 100644
--- a/README.md
+++ b/README.md
@@ -126,6 +126,7 @@ pkgs.krops.writeDeploy "deploy" {
   target = lib.mkTarget "user@host/path" // {
     extraOptions = [
       "-o" "LogLevel=DEBUG"
+      ["-i" "/path/to/identity/file"]
     ];
     sudo = true;
   };
@@ -697,21 +698,24 @@ for features spanning sources, such as flake inputs from sources, one for edge
 cases of flakes, such as unusual lock files, one for staying inside the target
 directory, whatever links it contains, and one for the arguments `writeDeploy`
 passes to `nixos-rebuild`.  After every deploy, all tests check that nothing
-outside the target directory changed.  The tests deploy every combination
-of a source type's options, except for patches, which the features test
-covers, to the deploying machine itself, to a remote target
-as `root`, and to a remote target using `sudo`, and check the result after
-deploying and after deploying again.  The scenarios whose results depend on
-the version of rsync also run with rsync 3.4.1 and 3.5.0, which
-`tests/rsync.nix` builds, whatever version nixpkgs has.
-The tests require KVM and nixpkgs with `pkgs.testers.runNixOSTest`
-(23.05 or later), and use `<nixpkgs>` by default.
+outside the target directory changed.  The tests deploy combinations of a
+source type's options to the deploying machine itself, to a remote target as
+`root`, and to a remote target using `sudo`, and check the result after
+deploying and after deploying again.  They cover every combination that a code
+path tells apart; the exhaustive tests add the remaining ones, e.g. drawing
+inputs combined with each of rsync's options.  Patches get covered by the
+features test.  The scenarios whose results depend on the version of rsync also
+run with rsync 3.4.1 and 3.5.0, which `tests/rsync.nix` builds, whatever
+version nixpkgs has.  The tests require KVM and nixpkgs with
+`pkgs.testers.runNixOSTest` (23.05 or later), and use `<nixpkgs>` by default.
 
 ```sh
-nix-build tests                 # all tests
-nix-build tests -A flake        # the test for one source type
-nix-build tests -A rsync-3-5-0  # the scenarios depending on rsync's version
-nix-build tests -A jq           # populate's programs for flakes, without VMs
+nix-build tests                   # all tests, except the exhaustive ones
+nix-build tests -A flake          # the test for one source type
+nix-build tests -A exhaustive     # all exhaustive tests
+nix-build tests -A exhaustive.git # the remaining combinations of one test
+nix-build tests -A rsync-3-5-0    # the scenarios depending on rsync's version
+nix-build tests -A jq             # populate's programs for flakes, without VMs
 ```