Eclipse Indigo “unable to connect to repository”

The three most influential factors for Eclipse speed are:

• Using the latest version of Eclipse (2020-06 as on 26 June 2020)
  Note that David Balažic's comment (July 2014) contradicts that criteria which was working six years ago:

The "same" workspace in Indigo (3.7.2) SR2 loads in 4 seconds, in Kepler SR2 (4.3.2) in 7 seconds and in Luna (4.4.0) in 10 seconds. All are Java EE bundles. Newer versions have more bundled plugins, but still the trend is obvious. (by "same" workspace I mean: same (additionally installed) plugins used, same projects checked out from version control).

• Launching it with the latest JDK (Java 14 at the time of writing, which does not prevent you to compile in your Eclipse project with any other JDK you want: 1.4.2, 1.5, 1.6 older...)

    -vm jdk1.6.0_10\jre\bin\client\jvm.dll
  

• Configuring the eclipse.ini (see this question for a complete eclipse.ini)

    -Xms512m
    -Xmx4096m
    [...]
  

The Xmx argument is the amount of memory Eclipse will get (in simple terms). With -Xmx4g, it gets 4 GB of RAM, etc.

Note:

1. Referring to the jvm.dll has advantages:

• Splash screen coming up sooner.
• Eclipse.exe in the process list instead of java.exe.
• Firewalls: Eclipse wants access to the Internet instead of Java.
• Window management branding issues, especially on Windows and Mac.

Dec. 2020, Udo conforms in the comments

From version 4.8 (Photon) an up there was a steady speed gain after each version.
The main platform was optimized every release to load faster, enable more features for the dark theme and to add more features for newer Java versions for the Java development tools.
Especially with-in the last 3 versions the startup time was increased a lot. There should be a significant increase in start-up time with the newest version of Eclipse 2020-12.

In my experience it started a lot faster with each new version.
But: There are still plug-ins which do not follow the new way of using the Eclipse API and are therefore still slow to start.
Since the change to Java 11 as the minimum runtime version starting from Eclipse version 2020-09 at least the core system uses the newer features of the JVM. It is up to the providers of the other plug-ins to upgrade to newer APIs and to use the full power of modern CPUs (e.g. concurrent programming model).

What you are trying to do is called a sparse checkout, and that feature was added in git 1.7.0 (Feb. 2012). The steps to do a sparse clone are as follows:

mkdir <repo>
cd <repo>
git init
git remote add -f origin <url>

This creates an empty repository with your remote, and fetches all objects but doesn't check them out. Then do:

git config core.sparseCheckout true

Now you need to define which files/folders you want to actually check out. This is done by listing them in .git/info/sparse-checkout, eg:

echo "some/dir/" >> .git/info/sparse-checkout
echo "another/sub/tree" >> .git/info/sparse-checkout

Last but not least, update your empty repo with the state from the remote:

git pull origin master

You will now have files "checked out" for some/dir and another/sub/tree on your file system (with those paths still), and no other paths present.

You might want to have a look at the extended tutorial and you should probably read the official documentation for sparse checkout and read-tree.

As a function:

function git_sparse_clone() (
  rurl="$1" localdir="$2" && shift 2

  mkdir -p "$localdir"
  cd "$localdir"

  git init
  git remote add -f origin "$rurl"

  git config core.sparseCheckout true

  # Loops over remaining args
  for i; do
    echo "$i" >> .git/info/sparse-checkout
  done

  git pull origin master
)

Usage:

git_sparse_clone "http://github.com/tj/n" "./local/location" "/bin"

Note that this will still download the whole repository from the server – only the checkout is reduced in size. At the moment it is not possible to clone only a single directory. But if you don't need the history of the repository, you can at least save on bandwidth by creating a shallow clone. See udondan's answer below for information on how to combine shallow clone and sparse checkout.

As of git 2.25.0 (Jan 2020) an experimental sparse-checkout command is added in git:

git sparse-checkout init
# same as: 
# git config core.sparseCheckout true

git sparse-checkout set "A/B"
# same as:
# echo "A/B" >> .git/info/sparse-checkout

git sparse-checkout list
# same as:
# cat .git/info/sparse-checkout