split是一个包含多个值的数组。然后调用split.map，它将遍历数组并对每个元素执行操作。
其中一个操作是latest_version = ...，这意味着对于数组中的每一个元素，你都在 * 重置 * latest_version的值，无论数组中的最后一个元素是什么，它最终都会定义latest_version的最终值，而这不是你想要的。
你也许可以使用类似这样的方法来实现你的目标：

# Set a regex that looks for:
# 1. v or V, optionally
# 2. one or more digits (e.g., 1 or 55)
# 3. a literal period and then one or more digits (e.g., 2 or 66)
# 4. a literal period and then one or more digits (e.g., 3 or 77), optionally
# This will match v1.2.3 or v1.2 or 1.2.3 or 1.2 or v10.1.2 or v10.1 or v10.1.20, etc.
# This will not match v1.2.3-alpha, for example
regex = /^[vV]?[0-9]+\.[0-9]+(\.[0-9]+)?$/

# Use the Rails repo as the sample as they have a ton of tags and a lot of variety
package_url = "https://github.com/rails/rails"

# Use a semantic variable name
git_versions = `git ls-remote --tags --refs #{package_url} "*\.*\.*"`

# Split the string by newlines
versions = git_versions.split("\n")

# Split each element by refs/tags/ and select the last element so that we get something like "v7.0.4" only 
versions = versions.map { |s| s.split('refs/tags/').last }

# Grab only the versions that match the regex, excluding things like "v6.0.2.rc2"
versions = versions.select { |s| s =~ regex }

# Remove all the v and Vs from the start of the version strings
versions = versions.map { |s| s.sub(/^[vV]/, '') }

# Convert all the strings to Gem::Version values
versions = versions.map { |s| Gem::Version.new(s) }

# Get the largest version
latest_version = versions.max

这段代码可以缩小很多，限制为数组的三次迭代，但从可读性的Angular 来看，这段代码并不出色：

regex = /^[vV]?[0-9]+\.[0-9]+(\.[0-9]+)?$/
package_url = "https://github.com/rails/rails"
git_versions = `git ls-remote --tags --refs #{package_url} "*\.*\.*"`
latest_version = git_versions.split("\n").map { |v| Gem::Version.create(v.split('refs/tags/').last.match(regex)&.[](0)&.sub(/^[vV]/, '')) }.compact.max
=> Gem::Version.new("7.0.4")