add dirname method for AzObject

Author: samtkaplan

docs/src/example.md

@@ -81,6 +81,9 @@ cp("mylocalfile.bin", io)
 io2 = open(AzContainer("foo"; storageaccount="mystorageaccount", session), "mycopyblob.bin")
 cp(io, io2)
 
+# get the container (similar to getting the root path of a POSIX filename)
+dirname(io)
+
 # remove the blob
 rm(io)
 ```

src/AzStorage.jl

@@ -102,6 +102,13 @@ write(io, rand(10))
 """
 Base.joinpath(container::AzContainer, name...) = open(container, join(name, '/'), false)
 
+"""
+    dirname(object::AzObject) -> AzContainer
+
+returns the container/prefix of the `object::AzObject`.
+"""
+Base.dirname(object::AzObject) = object.container
+
 """
     open(object::AzObject[, mode="w+"]) -> object
 

test/runtests.jl

@@ -396,6 +396,19 @@ end
     c = AzContainer(""; storageaccount="", session=session, nthreads=2, nretry=10)
     io = joinpath(c, "bar", "baz")
     @test isfile(io) == false
+    rm(c)
+end
+
+@testset "Object, dirname" begin
+    r = uuid4()
+    c = AzContainer("foo-$r-k", storageaccount=storageaccount, session=session, nthreads=2, nretry=10)
+    io = robust_joinpath(c, "bar", "baz")
+    _c = dirname(io)
+    @test isa(_c, AzContainer)
+    @test _c.storageaccount == c.storageaccount
+    @test _c.containername == c.containername
+    @test _c.prefix == c.prefix
+    rm(c)
 end
 
 @testset "Object, open" begin