Show methods for Signatures and Commits

Add `show` methods for `Signature` and `Commit`s in LibGit2.
Display the time of the commit using Julia's built-in date handling.

base/libgit2/commit.jl

@@ -22,6 +22,12 @@ function committer(c::GitCommit)
     return Signature(ptr)
 end
 
+function Base.show(io::IO, c::GitCommit)
+    authstr = sprint(show, author(c))
+    cmtrstr = sprint(show, committer(c))
+    print(io, "Commit Author: $authstr\nCommitter: $cmtrstr\nMessage:\n$(message(c))")
+end
+
 """ Wrapper around `git_commit_create` """
 function commit(repo::GitRepo,
                 refname::AbstractString,

base/libgit2/signature.jl

@@ -35,6 +35,8 @@ function Base.convert(::Type{GitSignature}, sig::Signature)
     return GitSignature(sig_ptr_ptr[])
 end
 
+Base.show(io::IO, sig::Signature) = print(io, "Name: $(sig.name), Email: $(sig.email), Time: $(Dates.unix2datetime(sig.time + sig.time_offset))")
+
 """Return signature object. Free it after use."""
 function default_signature(repo::GitRepo)
     sig_ptr_ptr = Ref{Ptr{SignatureStruct}}(C_NULL)

test/libgit2.jl

@@ -302,6 +302,12 @@ mktempdir() do dir
                     @test cmtr.time == test_sig.time
                     @test cmtr.email == test_sig.email
                     @test LibGit2.message(cmt) == commit_msg1
+                    showstr = split(sprint(show, cmt), "\n")
+                    # the time of the commit will vary so just test the first two parts
+                    @test contains(showstr[1], "Commit Author: Name: TEST, Email: [email protected], Time:")
+                    @test contains(showstr[2], "Committer: Name: TEST, Email: [email protected], Time:")
+                    @test showstr[3] == "Message:"
+                    @test showstr[4] == commit_msg1
                 finally
                     finalize(cmt)
                 end