Add diff-advance exercise

diff-advance/README.md

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+# Git Kata: Git Diff Advance
+
+## Setup
+
+Run `source setup.sh` or `bash setup.sh` or `./setup.sh` (or `.\setup.ps1` in PowerShell)
+
+## Tasks
+
+### Objectives: We will explore how git diff looks from different directions, `word-diff`, `name-only`, and a practical use case other than just to see diff.
+
+1. Current branch is `pipeline-improvement`. Use `git diff` to see how it is different from master.
+2. Compare `git diff master` and `git diff master pipeline-improvement`.
+3. Compare `git diff master pipeline-improvement` and `git diff pipeline-improvement master`. Notice what is being remove and added.
+4. Include `--word-diff` with `git diff`. In addition to the default, word diff can also be used in different modes, i.e. `--word-diff=color`. See how it is different from normal diff.
+5. Include `--name-only` option with `git diff` and see the result.
+6. With `--name-only`, we get a list of changed files. This can be useful for example when we want to do selective compile/test of changed files instead of a full re-build, given that steps can be compiled/tested independently. In our exercise, there are 3 steps in a pipeline and a utilities file. Let's say we only want to test the pipelines because we're confidence enough with the utils to not test it (naughty-list programmer). We can do something like this:
+
+    `git diff --name-only | grep .pipeline | xargs cat`
+
+    This will:
+    1. Get a list of the changed files
+    2. Filter for only `.pipeline` files
+    3. `cat`/test only these files
+
+## Relevant commands and options
+- `git diff`
+- `--word-diff`
+- `--name-only`
+- `grep`
+- `xargs`

diff-advance/setup.ps1

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+# Source utils
+. ..\utils\make-exercise-repo.ps1
+
+# Prep branches
+Set-Content -Value "Step 1 before changes" -Path step1.pipeline
+Set-Content -Value "Step 2 will remain unchanged" -Path step2.pipeline
+Set-Content -Value "Step 3 before changes" -Path step3.pipeline
+Set-Content -Value "Utilities before changes" -Path stepx.utils
+git add .
+git commit -m "Initial commit"
+
+git checkout -b pipeline-improvement
+Set-Content -Value "Step 1 after improvement" > step1.pipeline
+Set-Content -Value "Step 3 after changes" > step3.pipeline
+Set-Content -Value "Utilities after changes" > stepx.utils
+git add .
+git commit -m "Improve pipeline - name change"

diff-advance/setup.sh

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+#!/bin/bash
+
+# Source utils
+source ../utils/utils.sh
+
+# Prep repo
+kata="git-diff-advance"
+make-exercise-repo
+
+# Prep branches
+echo "Step 1 before changes" > step1.pipeline
+echo "Step 2 will remain unchanged" > step2.pipeline
+echo "Step 3 before changes" > step3.pipeline
+echo "Utilities before changes" > stepx.utils
+git add .
+git commit -m "Initial commit"
+
+git checkout -b pipeline-improvement
+echo "Step 1 after improvement" > step1.pipeline
+echo "Step 3 after changes" > step3.pipeline
+echo "Utilities after changes" > stepx.utils
+git add .
+git commit -m "Improve pipeline - name change"