From 8217737525f05b28359c17abeb0423ee3437c049 Mon Sep 17 00:00:00 2001
From: Petr Fedchenkov <giggsoff@gmail.com>
Date: Wed, 7 Sep 2022 11:25:44 +0300
Subject: [PATCH] Append dirty tag with content hash

To be able to identify successive file changes without commit, we should
 use their hash in tag alongside with dirty flag
 (<ls-tree>-dirty-<content hash>).

Signed-off-by: Petr Fedchenkov <giggsoff@gmail.com>
---
 src/cmd/linuxkit/pkglib/git.go    | 29 +++++++++++++++++++++++++++++
 src/cmd/linuxkit/pkglib/pkglib.go | 10 +++++++++-
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/cmd/linuxkit/pkglib/git.go b/src/cmd/linuxkit/pkglib/git.go
index 6286c8a1b..b51faeeed 100644
--- a/src/cmd/linuxkit/pkglib/git.go
+++ b/src/cmd/linuxkit/pkglib/git.go
@@ -3,10 +3,13 @@ package pkglib
 // Thin wrappers around git CLI invocations
 
 import (
+	"bufio"
+	"crypto/sha256"
 	"fmt"
 	"io"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"regexp"
 	"strings"
 
@@ -83,6 +86,32 @@ func (g git) isWorkTree(pkg string) (bool, error) {
 	return false, fmt.Errorf("unexpected output from git rev-parse --is-inside-work-tree: %s", tf)
 }
 
+func (g git) contentHash() (string, error) {
+	hash := sha256.New()
+	out, err := g.commandStdout(nil, "ls-files")
+	if err != nil {
+		return "", err
+	}
+	scanner := bufio.NewScanner(strings.NewReader(strings.TrimSpace(out)))
+	for scanner.Scan() {
+		f, err := os.Open(filepath.Join(g.dir, scanner.Text()))
+		if err != nil {
+			return "", err
+		}
+		if _, err := io.Copy(hash, f); err != nil {
+			_ = f.Close()
+			return "", err
+		}
+		if err = f.Close(); err != nil {
+			return "", err
+		}
+	}
+	if err = scanner.Err(); err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%x", hash.Sum(nil)), nil
+}
+
 func (g git) treeHash(pkg, commit string) (string, error) {
 	// we have to check if pkg is at the top level of the git tree,
 	// if that's the case we need to use tree hash from the commit itself
diff --git a/src/cmd/linuxkit/pkglib/pkglib.go b/src/cmd/linuxkit/pkglib/pkglib.go
index b66925290..5ddf43bd7 100644
--- a/src/cmd/linuxkit/pkglib/pkglib.go
+++ b/src/cmd/linuxkit/pkglib/pkglib.go
@@ -250,7 +250,15 @@ func NewFromCLI(fs *flag.FlagSet, args ...string) ([]Pkg, error) {
 				}
 
 				if dirty {
-					pkgHash += "-dirty"
+					contentHash, err := git.contentHash()
+					if err != nil {
+						return nil, err
+					}
+					if len(contentHash) < 7 {
+						return nil, fmt.Errorf("unexpected hash len: %d", len(contentHash))
+					}
+					// construct <ls-tree>-dirty-<content hash> tag
+					pkgHash += fmt.Sprintf("-dirty-%s", contentHash[0:7])
 				}
 			}
 		}