cmdutil

func MergeArgs ¶ added in v0.4.13

func MergeArgs(sets ...[]string) []string

This function merges argument sets left to right, so a later set overrides an earlier one. A token longer than one character and starting with "-" is a flag; following non-flag tokens are its values. A repeated flag keeps its first-seen position and takes its last-seen value list, so MergeArgs([]string{"-a", "-b", "2", "-b", "3"}) returns ["-a", "-b", "3"].

The --flag=value form splits on the first "=" and merges with the space form of the same flag; the emitted form follows the last-seen occurrence. Bare "-" and tokens with no flag open are positionals, passed through in place. A flag does not stay open across a set boundary.

The result is newly allocated and never aliases an input. It has a time complexity of O(n) in the total number of tokens.

This function infers flag arity positionally, because an argument list does not say which flags take a value. Two consequences:

• Repeatable flags collapse: ["-v", "-v"] returns ["-v"], and ["--header", "A", "--header", "B"] returns ["--header", "B"]. Do not use MergeArgs for tools whose flags accumulate.
• A trailing positional is absorbed as the preceding flag's value: ["--verbose", "file.txt"] parses file.txt as --verbose's value. There is no "--" terminator to guard against this.