Fix issue with Git Credential Manager for Windows (#30195)

- Ignores additional whitespace when reading in credentials.
- Warn when encountering unknown attributes. Should allow for more
  graceful failures in the future if the protocol is extended.

(cherry picked from commit 4b270b1)

stdlib/LibGit2/src/gitcredential.jl

@@ -1,5 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+const GIT_CRED_ATTRIBUTES = ("protocol", "host", "path", "username", "password", "url")
+
 """
     GitCredential
 
@@ -111,16 +113,19 @@ function Base.read!(io::IO, cred::GitCredential)
         else
             value = readuntil(io, '\n')
         end
+
         if key == "url"
             # Any components which are missing from the URL will be set to empty
             # https://git-scm.com/docs/git-credential#git-credential-codeurlcode
             Base.shred!(parse(GitCredential, value)) do urlcred
                 copy!(cred, urlcred)
             end
-        else
+        elseif key in GIT_CRED_ATTRIBUTES
             field = getproperty(cred, Symbol(key))
             field !== nothing && Symbol(key) == :password && Base.shred!(field)
             setproperty!(cred, Symbol(key), value)
+        elseif !all(isspace, key)
+            @warn "Unknown git credential attribute found: $(repr(key))"
         end
     end
 

stdlib/LibGit2/test/libgit2.jl

@@ -462,6 +462,45 @@ end
         Base.shred!(expected_cred)
     end
 
+    @testset "extra newline" begin
+        # The "Git for Windows" installer will also install the "Git Credential Manager for
+        # Windows" (https://github.com/Microsoft/Git-Credential-Manager-for-Windows) (also
+        # known as "manager" in the .gitconfig files). This credential manager returns an
+        # additional newline when returning the results.
+        str = """
+            protocol=https
+            host=example.com
+            path=
+            username=bob
+            password=*****
+
+            """
+        expected_cred = LibGit2.GitCredential("https", "example.com", "", "bob", "*****")
+
+        cred = read!(IOBuffer(str), LibGit2.GitCredential())
+        @test cred == expected_cred
+        @test sprint(write, cred) * "\n" == str
+        Base.shred!(cred)
+        Base.shred!(expected_cred)
+    end
+
+    @testset "unknown attribute" begin
+        str = """
+            protocol=https
+            host=example.com
+            attribute=value
+            username=bob
+            password=*****
+            """
+        expected_cred = LibGit2.GitCredential("https", "example.com", nothing, "bob", "*****")
+        expected_log = (:warn, "Unknown git credential attribute found: \"attribute\"")
+
+        cred = @test_logs expected_log read!(IOBuffer(str), LibGit2.GitCredential())
+        @test cred == expected_cred
+        Base.shred!(cred)
+        Base.shred!(expected_cred)
+    end
+
     @testset "use http path" begin
         cred = LibGit2.GitCredential("https", "example.com", "dir/file", "alice", "*****")
         expected = """