[PATCH] devshell: introduce intercepts as per native / nativesdk

[Paul Gortmaker <paul.gortmaker@windriver.com>]

In a devshell, recent versions of git will complain if the repo is owned
by someone other than the current UID - consider this example:

 ------
  bitbake -c devshell linux-yocto

  [...]

  kernel-source#git branch
  fatal: unsafe repository ('/home/paul/poky/build-qemuarm64/tmp/work-shared/qemuarm64/kernel-source' is owned by someone else)
  To add an exception for this directory, call:

        git config --global --add safe.directory /home/paul/poky/build-qemuarm64/tmp/work-shared/qemuarm64/kernel-source
  kernel-source#
 ------

Of course the devshell has UID zero and the "real" UID is for "paul" in
this case.  And so recent git versions complain.

As the whole purpose of the devshell is to invoke a shell where development
can take place, having a non-functional git is clearly unacceptable.

Richard suggested we could use PSEUDO_UNLOAD=1 to evade this issue, and I
suggested we probably will see other similar instances like this and should
make use of PATH to intercept via devshell wrappers - conveniently we already
have examples of this.

Here, we copy the existing "ar" example and tune it to the needs of git to
combine Richard's suggestion and mine.

As such we now also can store commit logs and use send-email with our user
specific settings, instead of "root", so in additon to fixing basic
commands like "git branch" it should also increase general usefulness.

Cc: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/meta/classes/devshell.bbclass b/meta/classes/devshell.bbclass
index 62dc958d9a4a..7ac134e0950f 100644
--- a/meta/classes/devshell.bbclass
+++ b/meta/classes/devshell.bbclass
@@ -2,6 +2,8 @@ inherit terminal
 
 DEVSHELL = "${SHELL}"
 
+PATH:prepend = "${COREBASE}/scripts/devshell-intercept:"
+
 python do_devshell () {
     if d.getVarFlag("do_devshell", "manualfakeroot"):
        d.prependVar("DEVSHELL", "pseudo ")
diff --git a/scripts/devshell-intercept/git b/scripts/devshell-intercept/git
new file mode 100755
index 000000000000..8adf5c9ecb71
--- /dev/null
+++ b/scripts/devshell-intercept/git
@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+#
+# Wrapper around 'git' that doesn't think we are root
+
+import os
+import shutil
+import sys
+
+os.environ['PSEUDO_UNLOAD'] = '1'
+
+# calculate path to the real 'git'
+path = os.environ['PATH']
+path = path.replace(os.path.dirname(sys.argv[0]), '')
+real_git = shutil.which('git', path=path)
+
+if len(sys.argv) == 1:
+    os.execl(real_git, 'git')
+
+os.execv(real_git, sys.argv)
-- 
2.17.1