Fix GitClientTest.test git diff when diff.noprefix=true is used

[deejgregor]

What Does This Do

This adds --no-prefix when ShellGitClient runs git diff, updates the regex in GitDiffParser, and adjusts test files.

Motivation

When diff.noprefix=true (or other git diff parameters that change the prefix format) used, it changes the output from git diff and and the test failure below is seen in GitClientTest.test git diff. I have used this git setting in my ~/.gitconfig file for years as it makes copying and pasting file names simpler.

java.lang.IllegalStateException: Line @@ -26 +26 @@ namespace Datadog.Trace.Logging contains changed lines information, but no changed file info is available
	at datadog.trace.civisibility.git.tree.GitDiffParser.parse(GitDiffParser.java:48)
	at datadog.trace.civisibility.utils.ShellCommandExecutor.executeCommand(ShellCommandExecutor.java:153)
	at datadog.trace.civisibility.utils.ShellCommandExecutor.executeCommand(ShellCommandExecutor.java:57)
	at datadog.trace.civisibility.git.tree.ShellGitClient.lambda$getGitDiff$18(ShellGitClient.java:926)
	at datadog.trace.civisibility.git.tree.ShellGitClient.executeCommand(ShellGitClient.java:980)
	at datadog.trace.civisibility.git.tree.ShellGitClient.getGitDiff(ShellGitClient.java:923)
	at datadog.trace.civisibility.git.tree.GitClientTest.test git diff(GitClientTest.groovy:264)

Additional Notes

Setting diff.noprefix=true changes the file name pattern and it fails to match GitDiffParser.CHANGED_FILE_PATTERN.

$ git diff | grep ^diff
diff --git a/dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/git/tree/ShellGitClient.java b/dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/git/tree/ShellGitClient.java

$ GIT_CONFIG_PARAMETERS="'diff.noprefix=true'" git diff | grep ^diff diff --git dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/git/tree/ShellGitClient.java dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/git/tree/ShellGitClient.java

Notice the lack of a/ and b/ on the latter output, but you'll see that the pattern expects that:

  private static final Pattern CHANGED_FILE_PATTERN =
      Pattern.compile("^diff --git a/(?<oldfilename>.+) b/(?<newfilename>.+)$");

The simple workaround is to pass --default-prefix to git diff, however this option has only been present since 2023: git/git@b39a569

A safer option would be to use --no-prefix, which has existed since 2007: git/git@eab9a40

To reproduce this error, you can run the test this way:

GIT_CONFIG_PARAMETERS="'diff.noprefix=true'" ./gradlew \
    --no-build-cache \
    :dd-java-agent:agent-ci-visibility:cleanTest \
    :dd-java-agent:agent-ci-visibility:test \
    --tests datadog.trace.civisibility.git.tree.GitClientTest

Contributor Checklist

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Jira ticket: [PROJ-IDENT]