scripts/git: Stop hard-coding the bash path in the git scripts

Some OSes don't have bash in /usr/bin, others have an ancient bash at
this path.

Fixes bug 30840; bugfix on 0.4.0.1-alpha.

changes/bug30840

@@ -0,0 +1,4 @@
+  o Minor bugfixes (git scripts):
+    - Stop hard-coding the bash path in the git scripts. Some OSes don't
+      have bash in /usr/bin, others have an ancient bash at this path.
+      Fixes bug 30840; bugfix on 0.4.0.1-alpha.

scripts/git/git-merge-forward.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 ##############################
 # Configuration (change me!) #

scripts/git/git-pull-all.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 ##################################
 # User configuration (change me) #

scripts/git/git-push-all.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # The remote upstream branch on which git.torproject.org/tor.git points to.
 UPSTREAM_BRANCH=${TOR_UPSTREAM_REMOTE_NAME:-"upstream"}

scripts/git/pre-commit.git-hook

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # To install this script, copy it to .git/hooks/pre-commit in local copy of
 # tor git repo and make sure it has permission to execute.

scripts/git/pre-push.git-hook

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # git pre-push hook script to:
 # 1) prevent "fixup!" and "squash!" commit from ending up in master, release-*