Drop xload_commit() in favor of git2go's Repository.LookupCommit()

This saves us one `git cat-file` call per recreated tag.

Time for restoring kirr/slapos.git from lab.nexedi.com backup

before: 10.3s
after:   8.9s

git-backup.go

@@ -285,16 +285,19 @@ func obj_represent_as_commit(sha1 Sha1, obj_type string) Sha1 {
 
 // recreate tag/tree/blob from specially crafted commit
 // (see obj_represent_as_commit() about how a objects are originally translated into commit)
-func obj_recreate_from_commit(commit_sha1 Sha1) {
+func obj_recreate_from_commit(g *git.Repository, commit_sha1 Sha1) {
     xraise  := func(info interface{})           { raise(&RecreateObjError{commit_sha1, info}) }
     xraisef := func(f string, a ...interface{}) { xraise(fmt.Sprintf(f, a...)) }
 
-    commit, _ := xload_commit(commit_sha1)
-    if len(commit.parentv) > 1 {
+    commit, err := g.LookupCommit(commit_sha1.AsOid())
+    if err != nil {
+        xraise(err)
+    }
+    if commit.ParentCount() > 1 {
         xraise(">1 parents")
     }
 
-    obj_type, obj_raw, err := headtail(commit.msg, "\n")
+    obj_type, obj_raw, err := headtail(commit.Message(), "\n")
     if err != nil {
         xraise("invalid encoded format")
     }
@@ -319,10 +322,10 @@ func obj_recreate_from_commit(commit_sha1 Sha1) {
         xraisef("encoded tag: %s", err)
     }
     if tag.tagged_type == "tag" {
-        if len(commit.parentv) == 0 {
+        if commit.ParentCount() == 0 {
             xraise("encoded tag corrupt (tagged is tag but []parent is empty)")
         }
-        obj_recreate_from_commit(commit.parentv[0])
+        obj_recreate_from_commit(g, Sha1FromOid(commit.ParentId(0)))
     }
 
     // verify consistency via re-encoding tag again
@@ -824,7 +827,7 @@ func cmd_restore_(gb *git.Repository, HEAD_ string, restorespecv []RestoreSpec)
             //   are not reachable from backup repo HEAD )
             for _, __ := range repo.refs {
                 if __.sha1 != __.sha1_ {
-                    obj_recreate_from_commit(__.sha1_)
+                    obj_recreate_from_commit(gb, __.sha1_)
                 }
             }
 

gitobjects.go

@@ -16,82 +16,14 @@ package main
 import (
     "errors"
     "fmt"
-    "strings"
 )
 
-type Commit struct {
-    tree    Sha1
-    parentv []Sha1
-    msg     string
-}
-
 type Tag struct {
     tagged_type string
     tagged_sha1 Sha1
     // TODO msg
 }
 
-// TODO Tree (if/when needed)
-// TODO Blob (if/when needed)
-
-// load/parse Commit
-
-// extract .tree .parent[] and .msg
-//
-// unfortunately `git show --format=%B` adds newline and optionally wants to
-// reencode commit message and otherwise heavily rely on rev-list traversal
-// machinery -> so we decode commit by hand in a plumbing way.
-func xload_commit(commit_sha1 Sha1) (commit *Commit, commit_raw string) {
-    gerr, commit_raw, _ := ggit("cat-file", "commit", commit_sha1, RunWith{raw: true})
-    if gerr != nil {
-        raise(&CommitLoadError{commit_sha1, gerr})
-    }
-    commit, err := commit_parse(commit_raw)
-    if err != nil {
-        raise(&CommitLoadError{commit_sha1, err})
-    }
-    return commit, commit_raw
-}
-
-type CommitLoadError struct {
-    commit_sha1 Sha1
-    err         error
-}
-
-func (e *CommitLoadError) Error() string {
-    return fmt.Sprintf("commit %s: %s", e.commit_sha1, e.err)
-}
-
-func commit_parse(commit_raw string) (*Commit, error) {
-    c := Commit{}
-    head, msg, err := headtail(commit_raw, "\n\n")
-    c.msg = msg
-    if err != nil {
-        return nil, errors.New("cannot split to head & msg")
-    }
-
-    headv := strings.Split(head, "\n")
-    if len(headv) == 0 {
-        return nil, errors.New("empty header")
-    }
-    _, err = fmt.Sscanf(headv[0], "tree %s\n", &c.tree)
-    if err != nil {
-        return nil, errors.New("bad tree entry")
-    }
-    for _, h := range headv[1:] {
-        if !strings.HasPrefix(h, "parent ") {
-            break
-        }
-        p := Sha1{}
-        _, err = fmt.Sscanf(h, "parent %s\n", &p)
-        if err != nil {
-            return nil, errors.New("bad parent entry")
-        }
-        c.parentv = append(c.parentv, p)
-    }
-    return &c, nil
-}
-
 // load/parse Tag
 func xload_tag(tag_sha1 Sha1) (tag *Tag, tag_raw string) {
     gerr, tag_raw, _ := ggit("cat-file", "tag", tag_sha1, RunWith{raw: true})