fix dispatches

src/plot.jl

@@ -90,9 +90,9 @@ function plot(args...; kw...)
 end
 
 # build a new plot from existing plots
-# note: we split into plt1 and plts_tail so we can dispatch correctly
+# note: we split into plt1, plt2 and plts_tail so we can dispatch correctly
-plot(plt1::Plot, plts_tail::Plot...; kw...) = plot!(deepcopy(plt1), deepcopy.(plts_tail)...; kw...)
+plot(plt1::Plot, plt2::Plot, plts_tail::Plot...; kw...) = plot!(deepcopy(plt1), deepcopy(plt2), deepcopy.(plts_tail)...; kw...)
-function plot!(plt1::Plot, plts_tail::Plot...; kw...)
+function plot!(plt1::Plot, plt2::Plot, plts_tail::Plot...; kw...)
     @nospecialize
     plotattributes = KW(kw)
     RecipesPipeline.preprocess_attributes!(plotattributes)
@@ -186,6 +186,7 @@ function plot!(args...; kw...)
 end
 
 # this adds to a specific plot... most plot commands will flow through here
+plot(plt::Plot, args...; kw...) = plot!(deepcopy(plt), args...; kw...)
 function plot!(plt::Plot, args...; kw...)
     @nospecialize
     plotattributes = KW(kw)

test/runtests.jl

@@ -30,6 +30,7 @@ end
 end # testset
 
 include("test_defaults.jl")
+include("test_pipeline.jl")
 include("test_axes.jl")
 include("test_axis_letter.jl")
 include("test_components.jl")

test/test_pipeline.jl

@@ -0,0 +1,10 @@
+using Plots, Test
+
+@testset "plot" begin
+    pl = plot(1:5)
+    pl2 = plot(pl, tex_output_standalone = true)
+    @test pl[:tex_output_standalone] == false
+    @test pl2[:tex_output_standalone] == true
+    plot!(pl, tex_output_standalone = true)
+    @test pl[:tex_output_standalone] == true
+end