[PATCH v2 2/4] git-p4: create new method gitRunHook

["Ben Keene via GitGitGadget" <gitgitgadget@gmail.com>]

From: Ben Keene <seraphire@gmail.com>

This commit is in preparation of introducing new p4 submit hooks.

The current code in the python script git-p4.py makes the assumption
that the git hooks can be executed by subprocess.call() method. However,
when git is run on Windows, this may not work as expected.

The subprocess.call() does not execute SH.EXE implictly under Windows,
so the scripts may fail. In other words, the hooks do not execute under
windows because the shell interpreter is not automatically loaded.

Add a new function, gitRunHook, that takes 2 parameters:
* the filename of an optionally registered git hook
* an optional list of parameters

The gitRunHook function will honor the existing behavior seen in the
current code for executing the p4-pre-submit hook:

* Hooks are looked for in core.hooksPath directory.
* If core.hooksPath is not set, then the current .git/hooks directory
  is checked.
* If the hook does not exist, the function returns True.
* If the hook file is not accessible, the function returns True.
* If the hook returns a zero exit code when executed, the function
  return True.
* If the hook returns a non-zero exit code, the function returns False.

Add new conditional behavior for Windows:
* Check for an evironment variable 'EXEPATH' which should be set by
  git when git-p4.py is envoked.
* If EXEPATH is None - treat it as an empty string.
* If EXEPATH is set, look for sh.exe in the bin/ directory located
  in EXEPATH.
* If EXEPATH is not set, attempt to resolve against "bin/sh.exe"
* Add a new test for Windows that checks to see of sh.exe can be
  located. If not, return True.

Signed-off-by: Ben Keene <seraphire@gmail.com>
---
 git-p4.py | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/git-p4.py b/git-p4.py
index 7d8a5ee788..4e481b3b55 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -4125,6 +4125,35 @@ def printUsage(commands):
     "unshelve" : P4Unshelve,
 }
 
+def gitRunHook(cmd, param=[]):
+    """Execute a hook if the hook exists."""
+    if verbose:
+        sys.stderr.write("Looking for hook: %s\n" % cmd)
+        sys.stderr.flush()
+
+    hooks_path = gitConfig("core.hooksPath")
+    if len(hooks_path) <= 0:
+        hooks_path = os.path.join(os.environ.get("GIT_DIR", ".git"), "hooks")
+
+    hook_file = os.path.join(hooks_path, cmd)
+    if isinstance(param,basestring):
+        param=[param]
+
+    if platform.system() == 'Windows':
+        exepath = os.environ.get("EXEPATH")
+        if exepath is None:
+            exepath = ""
+        shexe = os.path.join(exepath, "bin", "sh.exe")
+        if os.path.isfile(shexe) \
+            and os.path.isfile(hook_file) \
+            and os.access(hook_file, os.X_OK) \
+            and subprocess.call([shexe, hook_file] + param) != 0:
+            return False
+
+    else:
+        if os.path.isfile(hook_file) and os.access(hook_file, os.X_OK) and subprocess.call([hook_file] + param) != 0:
+            return False
+    return True
 
 def main():
     if len(sys.argv[1:]) == 0:
-- 
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