git-init.txt: move description section up

It's more or less standard that synopsis is followed by description,
then options.

This is not just a clean move though:

 - The paragraphs are realigned a bit
 - The text mentioning git-init-db is dropped. init-db is
   deprecated, no need to confuse new users

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-init.txt

@@ -11,6 +11,26 @@ SYNOPSIS
 'git init' [-q | --quiet] [--bare] [--template=<template_directory>] [--shared[=<permissions>]] [directory]
 
 
+DESCRIPTION
+-----------
+
+This command creates an empty git repository - basically a `.git`
+directory with subdirectories for `objects`, `refs/heads`,
+`refs/tags`, and template files.  An initial `HEAD` file that
+references the HEAD of the master branch is also created.
+
+If the `$GIT_DIR` environment variable is set then it specifies a path
+to use instead of `./.git` for the base of the repository.
+
+If the object storage directory is specified via the
+`$GIT_OBJECT_DIRECTORY` environment variable then the sha1 directories
+are created underneath - otherwise the default `$GIT_DIR/objects`
+directory is used.
+
+Running 'git init' in an existing repository is safe. It will not
+overwrite things that are already there. The primary reason for
+rerunning 'git init' is to pick up newly added templates.
+
 OPTIONS
 -------
 
@@ -74,32 +94,6 @@ line, the command is run inside the directory (possibly after creating it).
 --
 
 
-DESCRIPTION
------------
-This command creates an empty git repository - basically a `.git` directory
-with subdirectories for `objects`, `refs/heads`, `refs/tags`, and
-template files.
-An initial `HEAD` file that references the HEAD of the master branch
-is also created.
-
-If the `$GIT_DIR` environment variable is set then it specifies a path
-to use instead of `./.git` for the base of the repository.
-
-If the object storage directory is specified via the `$GIT_OBJECT_DIRECTORY`
-environment variable then the sha1 directories are created underneath -
-otherwise the default `$GIT_DIR/objects` directory is used.
-
-Running 'git init' in an existing repository is safe. It will not overwrite
-things that are already there. The primary reason for rerunning 'git init'
-is to pick up newly added templates.
-
-Note that 'git init' is the same as 'git init-db'.  The command
-was primarily meant to initialize the object database, but over
-time it has become responsible for setting up the other aspects
-of the repository, such as installing the default hooks and
-setting the configuration variables.  The old name is retained
-for backward compatibility reasons.
-
 TEMPLATE DIRECTORY
 ------------------