changeset 27935:594bdc380aa2 stable

subrepo: better error messages in _ensuregit

This patch improves the error messages raised when an OSError occurs, since
simply re-raising the exception can be both confusing and misleading. For
example, if "hg identify" is run inside a repository that contains a Git
subrepository and the git binary could not be found, it'll exit with the message
"abort: No such file or directory". That implies "identify" has a problem
reading the repository itself. There's no way for the user to know what the
real problem is unless they dive into the Mercurial source, which is what I
ended up doing after spending hours debugging errors while provisioning a VM
with Ansible (turns out I forgot to install Git on it).

Descriptive errors are especially important on Windows, since it's common for
Windows users to forget to set the "Path" system variable after installing Git.

--- a/mercurial/subrepo.py	Sat Jan 23 17:31:31 2016 +0800
+++ b/mercurial/subrepo.py	Sun Jan 17 22:53:57 2016 -0500
@@ -1294,10 +1294,25 @@
             self._gitexecutable = 'git'
             out, err = self._gitnodir(['--version'])
         except OSError as e:
-            if e.errno != 2 or os.name != 'nt':
-                raise
-            self._gitexecutable = 'git.cmd'
-            out, err = self._gitnodir(['--version'])
+            genericerror = _("error executing git for subrepo '%s': %s")
+            notfoundhint = _("check git is installed and in your PATH")
+            if e.errno != errno.ENOENT:
+                raise error.Abort(genericerror % (self._path, e.strerror))
+            elif os.name == 'nt':
+                try:
+                    self._gitexecutable = 'git.cmd'
+                    out, err = self._gitnodir(['--version'])
+                except OSError as e2:
+                    if e2.errno == errno.ENOENT:
+                        raise error.Abort(_("couldn't find 'git' or 'git.cmd'"
+                            " for subrepo '%s'") % self._path,
+                            hint=notfoundhint)
+                    else:
+                        raise error.Abort(genericerror % (self._path,
+                            e2.strerror))
+            else:
+                raise error.Abort(_("couldn't find git for subrepo '%s'")
+                    % self._path, hint=notfoundhint)
         versionstatus = self._checkversion(out)
         if versionstatus == 'unknown':
             self.ui.warn(_('cannot retrieve git version\n'))