tests: add reference files for julia@1.6.7

Some tests only run for older Julia versions,
these reference files are thus only generated
for the first time when run with an older julia
version.

Author: ReubenJ

test/reference_outputs/signatures_many_tuples_pre_110.txt

@@ -0,0 +1,9 @@
+
+```julia
+g()
+g(x)
+g(x, y)
+g(x, y, z; kwargs...)
+
+```
+

test/reference_outputs/signatures_pre_110.txt

@@ -0,0 +1,7 @@
+
+```julia
+g()
+g(x)
+
+```
+

test/reference_outputs/typed_method_signatures_64bit_pre_110.txt

@@ -0,0 +1,6 @@
+
+```julia
+h(x::Int64) -> Int64
+
+```
+

test/reference_outputs/typed_method_signatures_k7_all_16_versions.txt

@@ -0,0 +1,12 @@
+
+```julia
+k_7(
+    x::Union{Nothing, T} where T<:Integer
+) -> Union{Nothing, Integer}
+k_7(
+    x::Union{Nothing, T} where T<:Integer,
+    y::Integer
+) -> Union{Nothing, T} where T<:Integer
+
+```
+

test/tests.jl

@@ -119,11 +119,29 @@ ro_path(fn) = joinpath(@__DIR__, "reference_outputs", fn)
             str = @io2str with_test_repo() do
                 DSE.format(METHODLIST, ::IO, doc)
             end
-            remove_local_info = x -> replace(
-                x,
-                r"(defined at \[`).+(DocStringExtensions.jl/test/TestModule)" => s"\1[...]\2",
-                r"(tree/).+(/M)" => s"\1[...]\2"
-            )
+            # split into multiple replace() calls for older
+            # versions of julia where the replace(s, r => s, r => s...)
+            # method is missing
+            remove_local_info = x -> begin
+                x = replace(
+                    x,
+                    # remove the part of the path that precedes DocStringExtensions.jl/...
+                    # because it will differ per machine
+                    r"(defined at \[`).+(DocStringExtensions.jl/test/TestModule)" => s"\1[...]\2",
+                )
+                replace(
+                    x,
+                    # Remove the git hash because it will differ per
+                    # test run
+                    r"(tree/).+(/M)" => s"\1[...]\2"
+                )
+            end
+            # the replacements are needed because the local
+            # Git repo created by with_test_repo() will have
+            # a different commit hash each time the test suite is run
+            # and METHODLIST displays that. Reference tests will fail every
+            # time if we don't remove the hash and the local part of the 
+            # path
             @test_reference ro_path("method_lists.txt") remove_local_info(str)
         end