It simply has no effect.

Versions

• GitLens: 11.4.1
• VSCode: 1.55.2

Steps to Reproduce

• Set the value of gitlens.advanced.similarityThreshold to 10.

• mkdir similarity-index-threshold-test

• cd similarity-index-threshold-test

• git init

• Create a file named dummy.txt with the content:

  1
  2
  3
  4
  5
  6
  7
  8
  9
  10
  

• git add dummy.txt && git commit -m "Create file"

• Rename dummy.txt to dummy-new.txt.

• Edit dummy-new.txt so that it will become:

  1.
  2.
  3.
  4.
  5.
  6
  7
  8
  9
  10
  

• Stage your changes.

• From terminal, run git diff --cached -M10%. The output will be:

  diff --git a/dummy.txt b/dummy-new.txt
  similarity index 42%
  rename from dummy.txt
  rename to dummy-new.txt
  index f00c965..1f440aa 100644
  --- a/dummy.txt
  +++ b/dummy-new.txt
  @@ -1,8 +1,8 @@
  -1
  -2
  -3
  -4
  -5
  +1.
  +2.
  +3.
  +4.
  +5.
  6
  7
  8
  

• However, even though we set the value of gitlens.advanced.similarityThreshold to 10, which is the same as the value of the -M argument of the git-diff command that we have just ran, Source Control panel in Visual Studio Code will show dummy.txt as deleted, and dummy-new.txt as added, instead of showing dummy.txt to be renamed to dummy-new.txt.

• Now, remove the dot after 5 in dummy-new.txt. That is, edit dummy-new.txt so that it will become:

  1.
  2.
  3.
  4.
  5
  6
  7
  8
  9
  10
  

• Stage your changes. Now Source Control panel in Visual Studio Code will show the file as renamed. This is the proof that GitLens will always use 50% as the value of similarity index threshold, regardless of what we set as the value of gitlens.advanced.similarityThreshold.