New iteration behavior via FileIter and TreeWalker

Instead of returning a channel of files, Tree.Files() now returns a
FileIter with these qualities:

* It returns files in the original order of the repository (relying on a
* new Tree.OrderedNames property)
* It can return errors encountered when retrieving files and trees from
* underlying storage
* It can be Closed without having to drain the entire channel
* It defers the heavy lifting to a new TreeWalker type
* Its behavior is a little more consistent with other Iter types
* It's a little less prone to memory leaks

This update includes a new TreeWalker type that will iterate through all
of the entries of a tree and its descendant subtrees. It does the dirty
work that Tree.walkEntries() used to do, but with a public API.

A new TreeIter type is also included that just walks through subtrees.
This could be useful for performing a directory search while ignoring
files/blobs altogether.

1 files changed, 134 insertions, 0 deletions

diff --git a/tree_walker_test.go b/tree_walker_test.go
new file mode 100644
index 0000000..bdae79f
--- /dev/null
+++ b/tree_walker_test.go
@@ -0,0 +1,134 @@
+package git
+
+import (
+	"io"
+	"os"
+	"strconv"
+
+	"gopkg.in/src-d/go-git.v3/core"
+	"gopkg.in/src-d/go-git.v3/formats/packfile"
+
+	. "gopkg.in/check.v1"
+)
+
+type SuiteTreeWalker struct {
+	repos map[string]*Repository
+}
+
+var _ = Suite(&SuiteTreeWalker{})
+
+// create the repositories of the fixtures
+func (s *SuiteTreeWalker) SetUpSuite(c *C) {
+	fixtureRepos := [...]struct {
+		url      string
+		packfile string
+	}{
+		{"https://github.com/alcortesm/binary-relations.git", "formats/packfile/fixtures/alcortesm-binary-relations.pack"},
+		{"https://github.com/Tribler/dispersy.git", "formats/packfile/fixtures/tribler-dispersy.pack"},
+	}
+	s.repos = make(map[string]*Repository, 0)
+	for _, fixRepo := range fixtureRepos {
+		s.repos[fixRepo.url] = NewPlainRepository()
+
+		d, err := os.Open(fixRepo.packfile)
+		c.Assert(err, IsNil)
+
+		r := packfile.NewReader(d)
+		r.Format = packfile.OFSDeltaFormat // TODO: how to know the format of a pack file ahead of time?
+
+		_, err = r.Read(s.repos[fixRepo.url].Storage)
+		c.Assert(err, IsNil)
+
+		c.Assert(d.Close(), IsNil)
+	}
+}
+
+type treeWalkerExpectedEntry struct {
+	Kind core.ObjectType
+	Mode string
+	Name string
+	Hash string
+}
+
+func (s *SuiteTreeWalker) TestNext(c *C) {
+	for i, t := range []struct {
+		repo   string                    // the repo name as in localRepos
+		commit string                    // the commit to search for the file
+		objs   []treeWalkerExpectedEntry // the expected objects in the commit
+	}{
+		// https://api.github.com/repos/alcortesm/binary-relations/git/trees/b373f85fa2594d7dcd9989f4a5858a81647fb8ea
+		{"https://github.com/alcortesm/binary-relations.git", "b373f85fa2594d7dcd9989f4a5858a81647fb8ea", []treeWalkerExpectedEntry{
+			{core.BlobObject, "100644", ".gitignore", "7f41905b4d77ab4a9a2d334fcd0fb5db6e8e2183"},
+			{core.BlobObject, "100644", "Makefile", "d441e4e769b53cbd4b1215a1387f8c3108bac97d"},
+			{core.BlobObject, "100644", "binary-relations.tex", "cb50b067cc8cd9f639611d41416575c991ad8e97"},
+			{core.TreeObject, "040000", "imgs-gen", "b33007b7e83a738576c3f44369fe2f674bb23d5d"},
+			{core.TreeObject, "040000", "imgs-gen/simple-graph", "056633542b8ee990d6c89b7a812209dba13d6766"},
+			{core.BlobObject, "100644", "imgs-gen/simple-graph/Makefile", "49560402c1707f29c159ad14f369027250fb154a"},
+			{core.BlobObject, "100644", "imgs-gen/simple-graph/fig.fig", "2c414eb36f0c2e9a2f9c6382d85e63355752170c"},
+			{core.TreeObject, "040000", "src", "ec9d27c4df99caec3a817e9c018812a6c56c1b00"},
+			{core.TreeObject, "040000", "src/map-slice", "00cefb8e77f7a8c61b99dd2491ff48a3b0b16679"},
+			{core.BlobObject, "100644", "src/map-slice/map-slice.go", "12431e98381dd5097e1a19fe53429c72ef1f328e"},
+			{core.TreeObject, "040000", "src/simple-arrays", "9a3781b7fd9d2851e2a4488c035ed9ac905aec79"},
+			{core.BlobObject, "100644", "src/simple-arrays/simple-arrays.go", "104fbb4b0520c192f2e207a2dfd39162f6cdabf7"},
+		}},
+		// https://api.github.com/repos/Tribler/dispersy/git/trees/f5a1fca709f760bf75a7adaa480bf0f0e1a547ee
+		{"https://github.com/Tribler/dispersy.git", "f5a1fca709f760bf75a7adaa480bf0f0e1a547ee", []treeWalkerExpectedEntry{
+			{core.BlobObject, "100644", "__init__.py", "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391"},
+			{core.BlobObject, "100644", "authentication.py", "ca2fb017dce4506c4144ba81d3cbb70563487718"},
+			{core.BlobObject, "100644", "bloomfilter.py", "944e8ccc76779aad923f88f4a73b0d4e8999b6ea"},
+			{core.BlobObject, "100644", "bootstrap.py", "379a4400b992310f54ea56a4691760bdea8b1592"},
+			{core.BlobObject, "100644", "cache.py", "744d48dce50703e7d4ff14531ab2ab77e6b54685"},
+			{core.BlobObject, "100644", "callback.py", "f3a380cbe9eb1c02fb305f2bd2fc0fcfb103892f"},
+			{core.BlobObject, "100644", "candidate.py", "87309a51d3681bf6c46b22ce044dad41c97d32d2"},
+			{core.BlobObject, "100644", "community.py", "38226ffc2139a2349edaf016747d02b199508d41"},
+			{core.BlobObject, "100644", "conversion.py", "4e2fcefba40d99c2a6237768ed0fbb8e2e770c83"},
+			{core.BlobObject, "100644", "crypto.py", "8a6bb00df982fa806ce18838673ab1ef3fd52fed"},
+			{core.BlobObject, "100644", "database.py", "bb484bfd31a92f7775dbd3acf8740abf00bb3d74"},
+			{core.BlobObject, "100644", "debug.py", "3743f20d321f7b2b6d3b47211f93317818c3673e"},
+			{core.BlobObject, "100644", "debugcommunity.py", "1598ec5a773cc561430c5bb9b87157ef7d3e1c7c"},
+			{core.BlobObject, "100644", "decorator.py", "a1e913e674aec5402cc7b4e9fc0801e8155d2cec"},
+			{core.BlobObject, "100644", "destination.py", "d5c02588117d260e728d5c64aba885522ba508c5"},
+			{core.BlobObject, "100644", "dispersy.py", "63a08602e2ac8294b20543f0c89c75c740bf6c1c"},
+			{core.BlobObject, "100644", "dispersydatabase.py", "76dd222444c308c470efabde7ed511825004b4d3"},
+			{core.BlobObject, "100644", "distribution.py", "55a11beca7c09013f5b8ff46baa85b15948c756a"},
+			{core.BlobObject, "100644", "dprint.py", "fd6a8608d62bf415a65e78c9e1ca8df97513e598"},
+			{core.BlobObject, "100644", "encoding.py", "f29b0ebf65f06a0aa7b2ff1aea364f7889c58d56"},
+			{core.BlobObject, "100644", "endpoint.py", "5aa76efd3501de522dbdf2e6374440cf64131423"},
+			{core.BlobObject, "100644", "member.py", "c114c73f710b4c291305e353b4aa0106fafabd52"},
+			{core.BlobObject, "100644", "message.py", "e55bfe0efa851c4e94264dc745141f7f65b1d239"},
+			{core.BlobObject, "100644", "meta.py", "0f62db0fb93326daad6b4925a7d12155a1687f67"},
+			{core.BlobObject, "100644", "payload.py", "0aef13194c51dab3624665340b33dd4040516c86"},
+			{core.BlobObject, "100644", "requestcache.py", "7772c7d81b4b205970cac1a3cdabc2c2deb48b12"},
+			{core.BlobObject, "100644", "resolution.py", "525d6ec81c1fb098d2fe12ae0d5b10a368bfcace"},
+			{core.BlobObject, "100644", "script.py", "ef64e12cc1a4c0b3a5d42ff1b33adef202f30da3"},
+			{core.BlobObject, "100644", "singleton.py", "34662093edf45bbffa91125c13735e37410a185b"},
+			{core.BlobObject, "100644", "timeline.py", "826bb5e1802fb5eaf3144a9a195a994920101880"},
+			{core.TreeObject, "040000", "tool", "da97281af01b5b2dad1de6c84c5acb44da60ef7a"},
+			{core.BlobObject, "100644", "tool/__init__.py", "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391"},
+			{core.BlobObject, "100644", "tool/callbackscript.py", "eb9f8184ef08d9e031936e61bfa86fb9b45b965c"},
+			{core.BlobObject, "100644", "tool/scenarioscript.py", "245c41af66aab8f0a6fd00259b30a47f4d6c00dd"},
+		}},
+		{"https://github.com/Tribler/dispersy.git", "9d38ff85ca03adcf68dc14f5b68b8994f15229f4", []treeWalkerExpectedEntry(nil)},
+	} {
+		r := s.repos[t.repo]
+		commit, err := r.Commit(core.NewHash(t.commit))
+		c.Assert(err, IsNil, Commentf("subtest %d: %v (%s)", i, err, t.commit))
+
+		walker := NewTreeWalker(r, commit.Tree())
+		for k := 0; k < len(t.objs); k++ {
+			info := t.objs[k]
+			mode, err := strconv.ParseInt(info.Mode, 8, 32)
+			c.Assert(err, IsNil)
+			name, entry, obj, err := walker.Next()
+
+			c.Assert(err, IsNil, Commentf("subtest %d, iter %d, err=%v", i, k, err))
+			c.Assert(name, Equals, info.Name, Commentf("subtest %d, iter %d, name=%v, expected=%s, stack=%v, base=%v", i, k, name, info.Name, walker.stack, walker.base))
+			c.Assert(entry.Mode, Equals, os.FileMode(mode), Commentf("subtest %d, iter %d, entry.Mode=%v expected=%v", i, k, entry.Mode, mode))
+			c.Assert(obj.Type(), Equals, info.Kind, Commentf("subtest %d, iter %d, obj.Type()=%v expected=%v", i, k, obj.Type(), info.Kind))
+			c.Assert(entry.Hash.String(), Equals, info.Hash, Commentf("subtest %d, iter %d, entry.Hash=%v, expected=%s", i, k, entry.Hash, info.Hash))
+			c.Assert(obj.Hash().String(), Equals, info.Hash, Commentf("subtest %d, iter %d, obj.Hash()=%v, expected=%s", i, k, obj.Hash(), info.Hash))
+		}
+		_, _, _, err = walker.Next()
+		c.Assert(err, Equals, io.EOF)
+	}
+}