Add method to compute GitShortHash of a GitObject. (JuliaLang#20871)

Author: simonbyrne

base/libgit2/oid.jl

@@ -9,13 +9,23 @@ function GitHash(ptr::Ptr{UInt8})
     return oid_ptr[]
 end
 
+"""
+    GitHash(id::Vector{UInt8})
+
+Construct a `GitHash` from a vector of $OID_RAWSZ bytes.
+"""
 function GitHash(id::Array{UInt8,1})
     if length(id) != OID_RAWSZ
         throw(ArgumentError("invalid raw buffer size"))
     end
     return GitHash(pointer(id))
 end
 
+"""
+    GitHash(id::AbstractString)
+
+Construct a `GitHash` from a string of $OID_HEXSZ hexadecimal digits.
+"""
 function GitHash(id::AbstractString)
     bstr = String(id)
     len = sizeof(bstr)
@@ -27,6 +37,19 @@ function GitHash(id::AbstractString)
               (Ptr{GitHash}, Ptr{UInt8}, Csize_t), oid_ptr, bstr, len)
     return oid_ptr[]
 end
+
+function GitShortHash(buf::Buffer)
+    oid_ptr = Ref{GitHash}()
+    @check ccall((:git_oid_fromstrn, :libgit2), Cint,
+              (Ptr{GitHash}, Ptr{UInt8}, Csize_t), oid_ptr, buf.ptr, buf.size)
+    GitShortHash(oid_ptr[], buf.size)
+end
+
+"""
+    GitShortHash(id::AbstractString)
+
+Construct a `GitShortHash` from a string of at most $OID_HEXSZ hexadecimal digits.
+"""
 function GitShortHash(id::AbstractString)
     bstr = String(id)
     len = sizeof(bstr)
@@ -44,6 +67,15 @@ macro githash_str(id)
         GitHash(id)
     end
 end
+
+
+"""
+    GitHash(ref::GitReference)
+
+Get the identifier (`GitHash`) of the object referred to by the direct reference
+`ref`. Note: this does not work for symbolic references; in such cases use
+`GitHash(repo::GitRepo, ref_name::AbstractString)` instead.
+"""
 function GitHash(ref::GitReference)
     isempty(ref) && return GitHash()
     reftype(ref) != Consts.REF_OID && return GitHash()
@@ -52,6 +84,13 @@ function GitHash(ref::GitReference)
     return GitHash(oid_ptr)
 end
 
+
+"""
+    GitHash(repo::GitRepo, ref_name::AbstractString)
+
+Get the identifier (`GitHash`) of the object referred to by reference specified by
+`ref_name`.
+"""
 function GitHash(repo::GitRepo, ref_name::AbstractString)
     isempty(repo) && return GitHash()
     oid_ptr  = Ref(GitHash())
@@ -61,10 +100,31 @@ function GitHash(repo::GitRepo, ref_name::AbstractString)
     return oid_ptr[]
 end
 
+"""
+    GitHash(obj::GitObject)
+
+Get the identifier (`GitHash`) of `obj`.
+"""
 function GitHash(obj::GitObject)
     GitHash(ccall((:git_object_id, :libgit2), Ptr{UInt8}, (Ptr{Void},), obj.ptr))
 end
 
+"""
+    GitShortHash(obj::GitObject)
+
+Get a shortened identifier (`GitShortHash`) of `obj`. The minimum length (in characters)
+is determined by the `core.abbrev` config option, and will be of sufficient length to
+unambiuously identify the object in the repository.
+"""
+function GitShortHash(obj::GitObject)
+    buf_ref = Ref(Buffer())
+    @check ccall((:git_object_short_id, :libgit2), Cint,
+                 (Ptr{Buffer},Ptr{Void}), buf_ref, obj.ptr)
+    sid = GitShortHash(buf_ref[])
+    free(buf_ref)
+    return sid
+end
+
 Base.hex(id::GitHash) = join([hex(i,2) for i in id.val])
 Base.hex(id::GitShortHash) = hex(id.hash)[1:id.len]
 

base/libgit2/types.jl

@@ -22,13 +22,11 @@ end
 GitHash() = GitHash(ntuple(i->zero(UInt8), OID_RAWSZ))
 
 """
-    GitShortHash
+    GitShortHash(hash::GitHash, len::Integer)
 
-This is a shortened form of `GitHash`, which can be used to identify a git object when it
-is unique.
-
-Internally it is stored as two fields: a full-size `GitHash` (`hash`) and a length
-(`len`). Only the initial `len` hex digits of `hash` are used.
+A shortened git object identifier, which can be used to identify a git object when it is
+unique, consisting of the initial `len` hexadecimal digits of `hash` (the remaining digits
+are ignored).
 """
 struct GitShortHash <: AbstractGitHash
     hash::GitHash   # underlying hash: unused digits are ignored

test/libgit2.jl

@@ -473,6 +473,16 @@ mktempdir() do dir
                     @test !(short_oid1 < commit_oid1)
                     short_str = sprint(show, short_oid1)
                     @test short_str == "GitShortHash(\"$(string(short_oid1))\")"
+                    short_oid2 = LibGit2.GitShortHash(cmt)
+                    @test startswith(hex(commit_oid1), hex(short_oid2))
+
+                    cmt2 = LibGit2.GitCommit(repo, short_oid2)
+                    try
+                        @test commit_oid1 == LibGit2.GitHash(cmt2)
+                    finally
+                        close(cmt2)
+                    end
+
                     auth = LibGit2.author(cmt)
                     @test isa(auth, LibGit2.Signature)
                     @test auth.name == test_sig.name