From 39548a7712879446115dcf7621d2aa05b1ccdab3 Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Mon, 10 Oct 2022 20:35:23 -0500
Subject: [PATCH] Have tar handle / and .. at / as ./ and let -P retain ..

---
 tests/tar.test   |  6 ++++++
 toys/posix/tar.c | 24 ++++++++++++++----------
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/tests/tar.test b/tests/tar.test
index 5846ffbb..df63c2ff 100755
--- a/tests/tar.test
+++ b/tests/tar.test
@@ -324,6 +324,12 @@ testing "--xform" "$TAR one --xform=s@three/four/@zero@ | tar t | grep six" \
 rm -rf one
 SKIP=0
 
+testing '-P' "$TAR -P --no-recursion -C / /// .. | SUM 3" \
+  "a3e94211582da121845d823374d8f41ead62d7bd\n" "" ""
+
+testing 'without -P' "$TAR --no-recursion -C / /// .. | SUM 3" \
+  "077d03243e247b074806904885e6da272fd5857a\n" "" ""
+
 if false
 then
 # Sequencing issues that leak implementation details out the interface
diff --git a/toys/posix/tar.c b/toys/posix/tar.c
index 6930df8e..f75b33fd 100644
--- a/toys/posix/tar.c
+++ b/toys/posix/tar.c
@@ -239,18 +239,22 @@ static int add_to_tar(struct dirtree *node)
   if (S_ISDIR(st->st_mode) && name[i-1] != '/') strcat(name, "/");
 
   // remove leading / and any .. entries from saved name
-  if (!FLAG(P)) while (*hname == '/') hname++;
-  for (lnk = hname;;) {
-    if (!(lnk = strstr(lnk, ".."))) break;
-    if (lnk == hname || lnk[-1] == '/') {
-      if (!lnk[2]) goto done;
-      if (lnk[2]=='/') {
-        lnk = hname = lnk+3;
-        continue;
+  if (!FLAG(P)) {
+    while (*hname == '/') hname++;
+    for (lnk = hname;;) {
+      if (!(lnk = strstr(lnk, ".."))) break;
+      if (lnk == hname || lnk[-1] == '/') {
+        if (!lnk[2]) goto done;
+        if (lnk[2]=='/') {
+          lnk = hname = lnk+3;
+          continue;
+        }
       }
+      lnk += 2;
     }
-    lnk += 2;
+    if (!*hname) hname = "./";
   }
+
   if (!*hname) goto done;
 
   if (TT.warn && hname != name) {
@@ -881,7 +885,7 @@ static void trim2list(void *list, char *pline)
 
   dlist_add(list, n);
   if (i && n[i-1]=='\n') i--;
-  while (i && n[i-1] == '/') i--;
+  while (i>1 && n[i-1] == '/') i--;
   n[i] = 0;
 }
 
-- 
2.39.2