run-tests: introduce a `HGTEST_REAL_HG` variable for test

It turns out that currently, `hg` and `which hg` can point to different things
because `hg` is an alias… This is annoying because script and pieces of test
are unknowingly using the wrong `hg`.

We will fix it in another changeset. However some test actually need to use a
real `hg` binary and not some `chg` or `rhg` equivalent. So we introduce a new
variable with the right value and we put it to us in the appropriate location.

Differential Revision: https://phab.mercurial-scm.org/D11049

tests/run-tests.py

@@ -3160,10 +3160,12 b' class TestRunner(object):'
         if WINDOWS and not self._hgcommand.endswith(b'.exe'):
             self._hgcommand += b'.exe'
 
+        real_hg = os.path.join(self._bindir, self._hgcommand)
+        osenvironb[b'HGTEST_REAL_HG'] = real_hg
         # set CHGHG, then replace "hg" command by "chg"
         chgbindir = self._bindir
         if self.options.chg or self.options.with_chg:
-            osenvironb[b'CHGHG'] = os.path.join(self._bindir, self._hgcommand)
+            osenvironb[b'CHGHG'] = real_hg
         else:
             osenvironb.pop(b'CHGHG', None)  # drop flag for hghave
         if self.options.chg:
@@ -3182,9 +3184,7 b' class TestRunner(object):'
             # `--config` but that disrupts tests that print command lines and check expected
             # output.
             osenvironb[b'RHG_ON_UNSUPPORTED'] = b'fallback'
-            osenvironb[b'RHG_FALLBACK_EXECUTABLE'] = os.path.join(
-                self._bindir, self._hgcommand
-            )
+            osenvironb[b'RHG_FALLBACK_EXECUTABLE'] = real_hg
         if self.options.rhg:
             self._hgcommand = b'rhg'
         elif self.options.with_rhg:

tests/test-hghave.t

@@ -22,7 +22,7 b' Testing hghave extensibility for third p'
   > EOF
   $ ( \
   > testrepohgenv; \
-  > "$PYTHON" $TESTDIR/run-tests.py --with-hg=`which hg` -j 1 \
+  > "$PYTHON" $TESTDIR/run-tests.py --with-hg=$HGTEST_REAL_HG -j 1 \
   >    $HGTEST_RUN_TESTS_PURE test-hghaveaddon.t \
   > )
   running 1 tests using 1 parallel processes 

tests/test-run-tests.t

@@ -15,7 +15,7 b' Define a helper to avoid the install ste'
 =============
   $ rt()
   > {
-  >     "$PYTHON" $TESTDIR/run-tests.py --with-hg=`which hg` -j1 "$@"
+  >     "$PYTHON" $TESTDIR/run-tests.py --with-hg=$HGTEST_REAL_HG -j1 "$@"
   > }
 
 error paths
@@ -1369,7 +1369,7 b' Test globbing of local IP addresses'
 Add support for external test formatter
 =======================================
 
-  $ CUSTOM_TEST_RESULT=basic_test_result "$PYTHON" $TESTDIR/run-tests.py --with-hg=`which hg` -j1 "$@" test-success.t test-failure.t
+  $ CUSTOM_TEST_RESULT=basic_test_result "$PYTHON" $TESTDIR/run-tests.py --with-hg=$HGTEST_REAL_HG -j1 "$@" test-success.t test-failure.t
   running 2 tests using 1 parallel processes 
   
   # Ran 2 tests, 0 skipped, 0 failed.