| 1 | package tinygit |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "errors" |
| 6 | "fmt" |
| 7 | "strings" |
| 8 | "time" |
| 9 | ) |
| 10 | |
| 11 | const collaborationDiffBytes = 512 * 1024 |
| 12 | const collaborationDiffTimeout = 5 * time.Second |
| 13 | |
| 14 | // CollaborationDiff is the result of rendering a pull request's local Git |
| 15 | // objects. Status is "ok" when Diff is authoritative and |
| 16 | // "diff_unavailable" when one or both commits are not present locally. |
| 17 | type CollaborationDiff struct { |
| 18 | Status string `json:"status"` |
| 19 | Base string `json:"base,omitempty"` |
| 20 | Tip string `json:"tip,omitempty"` |
| 21 | MergeBase string `json:"merge_base,omitempty"` |
| 22 | Diff string `json:"diff,omitempty"` |
| 23 | Truncated bool `json:"truncated,omitempty"` |
| 24 | Reason string `json:"reason,omitempty"` |
| 25 | } |
| 26 | |
| 27 | // PRDiff renders a bounded diff from commits already present in the |
| 28 | // repository. It never fetches or resolves a remote ref. A supplied base is |
| 29 | // used only after it is verified as a local commit; when it is empty, Git's |
| 30 | // merge-base with the repository target is used. |
| 31 | func (g *GitRelay) PRDiff(ctx context.Context, r Repository, base, tip string) CollaborationDiff { |
| 32 | ctx, cancel := context.WithTimeout(ctx, collaborationDiffTimeout) |
| 33 | defer cancel() |
| 34 | result := CollaborationDiff{Status: "diff_unavailable" , Base: base, Tip: tip} |
| 35 | if !isObjectID(base) && base != "" { |
| 36 | result.Reason = "invalid base commit" |
| 37 | return result |
| 38 | } |
| 39 | if !isObjectID(tip) { |
| 40 | result.Reason = "invalid tip commit" |
| 41 | return result |
| 42 | } |
| 43 | if err := g.localCommit(ctx, r, tip); err != nil { |
| 44 | result.Reason = "tip commit is unavailable locally" |
| 45 | return result |
| 46 | } |
| 47 | if base != "" { |
| 48 | if err := g.localCommit(ctx, r, base); err != nil { |
| 49 | result.Reason = "base commit is unavailable locally" |
| 50 | return result |
| 51 | } |
| 52 | } |
| 53 | target, err := g.targetCommit(ctx, r) |
| 54 | if err != nil { |
| 55 | result.Reason = "repository target commit is unavailable locally" |
| 56 | return result |
| 57 | } |
| 58 | if base != "" { |
| 59 | // A PR base is meaningful only when it is reachable from both sides of |
| 60 | // the comparison. Checking the current target as well prevents an old |
| 61 | // or malicious PR-only ancestor from being presented as the repository |
| 62 | // diff base. |
| 63 | if err := g.browseCommand(ctx, r, "merge-base" , "--is-ancestor" , base, tip).Run(); err != nil { |
| 64 | result.Reason = "base is not an ancestor of tip" |
| 65 | return result |
| 66 | } |
| 67 | if err := g.browseCommand(ctx, r, "merge-base" , "--is-ancestor" , base, target).Run(); err != nil { |
| 68 | result.Reason = "base is not an ancestor of repository target" |
| 69 | return result |
| 70 | } |
| 71 | result.MergeBase = base |
| 72 | } else { |
| 73 | b, err := g.browseCommand(ctx, r, "merge-base" , "--" , tip, target).Output() |
| 74 | if err != nil || !isObjectID(strings.TrimSpace(string(b))) { |
| 75 | result.Reason = "merge base is unavailable locally" |
| 76 | return result |
| 77 | } |
| 78 | result.MergeBase = strings.TrimSpace(string(b)) |
| 79 | result.Base = result.MergeBase |
| 80 | } |
| 81 | |
| 82 | b, truncated, err := readBrowseOutput(g.browseCommand(ctx, r, "diff" , "--format=" , "--no-ext-diff" , "--no-textconv" , "--no-renames" , "--binary" , result.MergeBase, tip, "--" ), collaborationDiffBytes) |
| 83 | if err != nil { |
| 84 | result.Reason = "unable to render local diff" |
| 85 | return result |
| 86 | } |
| 87 | result.Status = "ok" |
| 88 | result.Diff = strings.ToValidUTF8(string(b), "�" ) |
| 89 | result.Truncated = truncated |
| 90 | return result |
| 91 | } |
| 92 | |
| 93 | func (g *GitRelay) targetCommit(ctx context.Context, r Repository) (string, error) { |
| 94 | target := strings.TrimPrefix(r.Head, "ref: " ) |
| 95 | if target == "" || !validBrowsePath(target) { |
| 96 | return "" , errors.New("missing repository target" ) |
| 97 | } |
| 98 | b, err := g.browseCommand(ctx, r, "rev-parse" , "--verify" , "--end-of-options" , target+"^{commit}" ).Output() |
| 99 | if err != nil { |
| 100 | return "" , err |
| 101 | } |
| 102 | target = strings.TrimSpace(string(b)) |
| 103 | if !isObjectID(target) || g.localCommit(ctx, r, target) != nil { |
| 104 | return "" , errors.New("target commit unavailable" ) |
| 105 | } |
| 106 | return target, nil |
| 107 | } |
| 108 | |
| 109 | func (g *GitRelay) localCommit(ctx context.Context, r Repository, oid string) error { |
| 110 | if !isObjectID(oid) { |
| 111 | return errors.New("invalid object id" ) |
| 112 | } |
| 113 | b, err := g.browseCommand(ctx, r, "cat-file" , "-t" , oid).Output() |
| 114 | if err != nil || strings.TrimSpace(string(b)) != "commit" { |
| 115 | return fmt.Errorf("commit unavailable: %s" , oid) |
| 116 | } |
| 117 | return nil |
| 118 | } |