[PATCH] submodule documentation: Rewrite introductory paragraphs

[Stefan Beller <sbeller@google.com>]

It's better to start the man page with a description of what submodules
actually are instead of saying what they are not.

Reorder the paragraphs such that
the first short paragraph introduces the submodule concept,
the second paragraph highlights the usage of the submodule command,
the third paragraph giving background information,
and finally the fourth paragraph discusing alternatives such
as subtrees and remotes, which we don't want to be confused with.

This ordering deepens the knowledge on submodules with each paragraph.
First the basic questions like "How/what" will be answered, while the
underlying concepts will be taught at a later time.

Making sure it is not confused with subtrees and remotes is not really
enhancing knowledge of submodules itself, but rather painting the big
picture of git concepts, so you could also argue to have it as the second
paragraph. Personally I think this may confuse readers, specially newcomers
though.

Signed-off-by: Stefan Beller <sbeller@google.com>
---

I rewrote the first 2 paragraphs as well now. I think it doesn't make sense
to mention any subcommand in the description section, so I removed 
 "When adding a new submodule to the tree, the 'add' subcommand is to be used."
though I kept the warning about submodules not being autmatically updated by
clone and pull. All other subcommands are gone from the description.


>> Not a new problem, but does the command really "manage them for
>> you"?  I view it more like "You can use this command to manage,
>> inspect and update the submodules".
>
> I agree.

Trying to find a better wording I looked more closely at other man pages to get
consistent with them. Most of them (e.g. add, status, rebase, revert) just describe
what they do in a short manner.

Now I am looking at the subtree man page and it looks as if it written in a similar style
to the submodules man page, the first 2 paragraphs give a short description what
subtrees do (not the command, but the concept) including an example.
The third paragraph then starts with "Subtrees are not to be confused
with submodules, ..." which I'd not want to see as early in a man page.
So in the subtree man page there is no such paragraph as
 
    This command can do this and that.

but rather the concept and examples are given.

 Documentation/git-submodule.txt | 50 ++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 2c25916..97718cf 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -25,22 +25,17 @@ SYNOPSIS
 
 DESCRIPTION
 -----------
-Submodules allow foreign repositories to be embedded within
-a dedicated subdirectory of the source tree, always pointed
-at a particular commit.
+This command will inspect, update and manage submodules.
 
-They are not to be confused with remotes, which are meant mainly
-for branches of the same project; submodules are meant for
-different projects you would like to make part of your source tree,
-while the history of the two projects still stays completely
-independent and you cannot modify the contents of the submodule
-from within the main project.
-If you want to merge the project histories and want to treat the
-aggregated whole as a single project from then on, you may want to
-add a remote for the other project and use the 'subtree' merge strategy,
-instead of treating the other project as a submodule. Directories
-that come from both projects can be cloned and checked out as a whole
-if you choose to go that route.
+Submodules allow you to keep another Git repository in a subdirectory
+of your repository. The other repository has its own history, which does not
+interfere with the history of the current repository. This can be used to
+have external dependencies such as libraries for example.
+
+When cloning or pulling a repository containing submodules however,
+these will not be checked out by default; the 'init' and 'update'
+subcommands will maintain submodules checked out and at
+appropriate revision in your working tree.
 
 Submodules are composed from a so-called `gitlink` tree entry
 in the main repository that refers to a particular commit object
@@ -51,19 +46,18 @@ describes the default URL the submodule shall be cloned from.
 The logical name can be used for overriding this URL within your
 local repository configuration (see 'submodule init').
 
-This command will manage the tree entries and contents of the
-gitmodules file for you, as well as inspect the status of your
-submodules and update them.
-When adding a new submodule to the tree, the 'add' subcommand
-is to be used.  However, when pulling a tree containing submodules,
-these will not be checked out by default;
-the 'init' and 'update' subcommands will maintain submodules
-checked out and at appropriate revision in your working tree.
-You can briefly inspect the up-to-date status of your submodules
-using the 'status' subcommand and get a detailed overview of the
-difference between the index and checkouts using the 'summary'
-subcommand.
-
+Submodules are not to be confused with remotes, which are meant
+mainly for branches of the same project; submodules are meant for
+different projects you would like to make part of your source tree,
+while the history of the two projects still stays completely
+independent and you cannot modify the contents of the submodule
+from within the main project.
+If you want to merge the project histories and want to treat the
+aggregated whole as a single project from then on, you may want to
+add a remote for the other project and use the 'subtree' merge strategy,
+instead of treating the other project as a submodule. Directories
+that come from both projects can be cloned and checked out as a whole
+if you choose to go that route.
 
 COMMANDS
 --------
-- 
2.4.0.194.gc518059