Fix tar regular expr and improve related test

It seems GNAT's Normalize_Arguments does its own escaping, so we do not need to
do it ourselves. Also, the test checks that indeed the `alire` folder is
excluded when tar'ing manually.

src/alire/alire-publish.adb

@@ -331,22 +331,24 @@ package body Alire.Publish is
             & "cfj"
             & Archive --  Destination file at alire/archives/crate-version.tbz2
 
+            & String'("--exclude=./alire")
+            --  Exclude top-level alire folder, before applying prefix
+
             --  exclude .git and the like, with workaround for macOS bsd tar
             & (if GNATCOLL.OS.Constants.OS in GNATCOLL.OS.MacOS
                then Empty_Vector
-                    & "--exclude='./.git'"
-                    & "--exclude='./.hg'"
-                    & "--exclude='./.svn'"
-                    & String'("-s,^\./," & Milestone & "/,")
+                    & "--exclude=./.git"
+                    & "--exclude=./.hg"
+                    & "--exclude=./.svn"
+                    & String'("-s,^./," & Milestone & "/,")
                     --  Prepend empty milestone dir as required for our tars)
               else Empty_Vector
                     & "--exclude-backups"      -- exclude .#* *~ #*# patterns
                     & "--exclude-vcs"          -- exclude .git, .hg, etc
                     & "--exclude-vcs-ignores"  -- exclude from .gitignore, etc
-                    & String'("--transform=s,^\./," & Milestone & "/,"))
+                    & String'("--transform=s,^./," & Milestone & "/,"))
                     --  Prepend empty milestone dir as required for our tars
 
-            & "--exclude='./alire'" -- exclude top-level alire folder
             & ".");
          pragma Warnings (On);
       end Tar_Archive;

testsuite/tests/publish/tarball-plaindir/test.py

@@ -3,21 +3,36 @@
 """
 
 from drivers.alr import init_local_crate, run_alr
+from glob import glob
 from shutil import copyfile
 from subprocess import run
 
+import drivers.helpers
 import os
 
 # Prepare our "remote" repo
 init_local_crate("xxx", enter=True)
 
+canary = "canary.txt"
+
+# Create a canary file to double-check that it does not make into the tarball
+with open(os.path.join("alire", canary), "wt") as file:
+    print(file, "...\n")
+
 # Publish it. We need to give input to alr, so we directly call it. We use the
 # generated location as the "online" location, and this works because we are
 # forcing.
 p = run(["alr", "publish", "--skip-build", "--tar", "-q", "-f", "-n"],
         input=f"file:{os.getcwd()}/alire/archives/xxx-0.0.0.tbz2\n".encode())
 p.check_returncode()
 
+# Verify the generated file does not contain the alire folder
+p = run(["tar", "tf", "alire/archives/xxx-0.0.0.tbz2"],
+        capture_output=True)
+p.check_returncode()
+assert "xxx-0.0.0/alire/" not in p.stdout.decode(), \
+    "Unexpected contents in tarball: " + p.stdout.decode()
+
 # Verify the index manifest has been generated
 assert os.path.isfile("./alire/releases/xxx-0.0.0.toml")
 
@@ -30,4 +45,8 @@
 
 run_alr("get", "--build", "xxx")  # Should not err
 
+# Verify the canary didn't made through
+os.chdir(glob("xxx*")[0])
+assert not os.path.isfile(os.path.join("alire", canary))
+
 print('SUCCESS')