sync: Support authentication to manifest server with .netrc

When using the --smart-sync or --smart-tag option, and the specified
manifest server is hosted on a server that requires authentication,
repo sync fails with the error: HTTP 401 Unauthorized.

Add support for getting the credentials from the .netrc file.

If a .netrc file exists in the user's home directory, and it contains
credentials for the hostname of the manifest server specified in the
manifest, use the credentials to authenticate with the manifest server
using the URL syntax extension for Basic Authentication:

  http://user:password@host:port/path

Credentials from the .netrc file are only used if the manifest server
URL specified in the manifest does not already include credentials.

Change-Id: I06e6586e8849d0cd12fa9746789e8d45d5b1f848
Clean up imports

manifest_xml: import `HEAD` and `R_HEADS` from correct module
version: import `HEAD` from correct module

`HEAD` and `R_HEADS` should be imported from the git_refs module,
where they are originally defined, rather than from the project
module.

repo: remove unused import of readline

cherry_pick: import standard modules on separate lines
smartsync: import subcmd modules explicitly from subcmd

Use:
  `import re
  import sys`
and
  `from subcmds.sync import Sync`

Instead of:
  `import sys, re`
and
  `from sync import Sync`

Change-Id: Ie10dd6832710939634c4f5c86b9ba5a9cd6fc92e
sync: Support manual authentication to the manifest server

Add two new command line options, -u/--manifest-server-username and
-p/--manifest-server-password, which can be used to specify a username
and password to authenticate to the manifest server when using the
-s/--smart-sync or -t/--smart-tag option.

If -u and -p are not specified when using the -s or -t option, use
authentication credentials from the .netrc file (if there are any).

Authentication credentials from -u/-p or .netrc are not used if the
manifest server specified in the manifest file already includes
credentials.

Change-Id: I6cf9540d28f6cef64c5694e8928cfe367a71d28d
Fix incorrect default_groups when parsing projects from XML manifest

Change Details:
* Switch first default group to 'all' instead of 'default'

Change Benefits:
* More consistent with default_groups in the counterpart Save() function
* Fixes bug where command 'repo manifest' added an extra 'default'
  group to every output project element groups attribute. This bug was
  particularly confusing for projects which had 'groups="notdefault"'
  as they were output as 'groups="notdefault,default"' by 'repo manifest'

Change-Id: I5611c027a982d3394899466248b971910bec8c6b
manifest: record the original revision when in -r mode.

Currently when doing a sync against a revision locked manifest,
sync has no option but to fall back to sync'ing the entire refs space;
it doesn't know which ref to ask for that contains the sha1 it wants.

This sucks if we're in -c mode; thus when we generate a revision
locked manifest, record the originating branch- and try syncing that
branch first.  If the sha1 is found within that branch, this saves
us having to pull down the rest of the repo- a potentially heavy
saving.

If that branch doesn't have the desired sha1, we fallback to sync'ing
everything.

Change-Id: I99a5e44fa1d792dfcada76956a2363187df94cf1
Merge "manifest: record the original revision when in -r mode."
Remove `ImportError` class

The definition of `ImportError` redefines the Python built-in
class of the same name.

It is not used anywhere, so remove it.

Change-Id: I557ce28c93a3306fff72873dc6f477330fc33128
Correct call to `sys.exit()`

It should be `sys.exit()` not `os.exit()`.

Change-Id: Iaeeef456ddf2d17f5df2b712e50e3630bed856c3
Update commit-msg hook to version from Gerrit v2.5-rc0

Change-Id: I0d11ac0c24cd53386e996b7dd9bd37c89c789f60
Remove unreachable code

Change 9bb1816b removed part of a block of code, but left the
remaining part unreachable.  Remove it.

Change-Id: Icdc6061d00e6027df32dee9a3bad3999fe7cdcbc
Expand ~ to user's home directory for --reference

This allows a user to have a 'repo init' as:
  $ repo init -u ... --reference=~/mirror

Change-Id: Ib85b7c8ffca9d732132c68fe9a8d7f0ab1fa9288
Coding style cleanup

Fix the following issues reported by pylint:

C0321: More than one statement on a single line
W0622: Redefining built-in 'name'
W0612: Unused variable 'name'
W0613: Unused argument 'name'
W0102: Dangerous default value 'value' as argument
W0105: String statement has no effect

Also fixed a few cases of inconsistent indentation.

Change-Id: Ie0db839e7c57d576cff12d8c055fe87030d00744
Merge "Expand ~ to user's home directory for --reference"
Merge "Coding style cleanup"
Rename "dir" variables

The variable name "dir" conflicts with the name of a Python built-in
function: http://docs.python.org/library/functions.html#dir

Change-Id: I850f3ec8df7563dc85e21f2876fe5e6550ca2d8f
Support HTTP authentication using user input as fallback

If repo could not find authentication credentials from ~/.netrc, this
patch tries to get user and password from user's console input. This
could be a good choice if user doesn't want to save his plain password
in ~/.netrc or if user doesn't know about the netrc usage.

The user will be prompted only if authentication infomation does not
exist in the password manager. Since main.py firstly loads auth
infomation from ~/.netrc, this will be executed only as fallback
mechanism.

Example:
$ repo upload .
Upload project xxx/ to remote branch master:
 branch yyy ( 1 commit, ...):
 to https://review.zzz.com/gerrit/ (y/N)? y

(repo may try to access to https://review.zzz.com/gerrit/ssh_info and
will get the 401 HTTP Basic Authentication response from server. If no
authentication info in ~/.netrc, This patch will ask username/passwd)

Authorization Required (Message from Web Server)
User: pororo
Password:
....
[OK ] xxx/

Change-Id: Ia348a4609ac40060d9093c7dc8d7c2560020455a
More coding style cleanup

Fixing more issues found with pylint.  Some that were supposed to
have been fixed in the previous sweep (Ie0db839e) but were missed:

C0321: More than one statement on a single line
W0622: Redefining built-in 'name'

And some more:

W0631: Using possibly undefined loop variable 'name'
W0223: Method 'name' is abstract in class 'name' but is not overridden
W0231: __init__ method from base class 'name' is not called

Change-Id: Ie119183708609d6279e973057a385fde864230c3
Represent git-submodule as nested projects

We need a representation of git-submodule in repo; otherwise repo will
not sync submodules, and leave workspace in a broken state.  Of course
this will not be a problem if all projects are owned by the owner of the
manifest file, who may simply choose not to use git-submodule in all
projects.  However, this is not possible in practice because manifest
file owner is unlikely to own all upstream projects.

As git submodules are simply git repositories, it is natural to treat
them as plain repo projects that live inside a repo project.  That is,
we could use recursively declared projects to denote the is-submodule
relation of git repositories.

The behavior of repo remains the same to projects that do not have a
sub-project within.  As for parent projects, repo fetches them and their
sub-projects as normal projects, and then checks out subprojects at the
commit specified in parent's commit object.  The sub-project is fetched
at a path relative to parent project's working directory; so the path
specified in manifest file should match that of .gitmodules file.

If a submodule is not registered in repo manifest, repo will derive its
properties from itself and its parent project, which might not always be
correct.  In such cases, the subproject is called a derived subproject.

To a user, a sub-project is merely a git-submodule; so all tips of
working with a git-submodule apply here, too.  For example, you should
not run `repo sync` in a parent repository if its submodule is dirty.

Change-Id: I541e9e2ac1a70304272dbe09724572aa1004eb5c
Add pylint configuration and instructions

pylint configuration file (.pylintrc) is added, and submission
instructions are updated to include pylint usage steps.

Deprecated pylint suppression (`disable-msg`) is updated in a few
modules to make it work properly with the latest version (0.26).

Change-Id: I4ec2ef318e23557a374ecdbf40fe12645766830c
Change PyDev project version to "python 2.6"

Repo is dropping support for Python <2.5 soon, so this updates the
PyDev configuration appropriately.

Change-Id: If327951e3a9fd9ff7513b931bfcfe6172dc8e4c5