cli/command/container: use local copy of pkg/system.IsAbs

[thaJeztah]

• relates to Decouple pkg/archive from pkg/system moby/moby#49072

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 59.52%. Comparing base (91d097e) to head (1eda498).
Report is 20 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5697   +/-   ##
=======================================
  Coverage   59.51%   59.52%           
=======================================
  Files         346      346           
  Lines       29379    29381    +2     
=======================================
+ Hits        17486    17488    +2     
  Misses      10923    10923           
  Partials      970      970           

[thaJeztah]

Actually wondering now if we should share the implementation from the compose-loader, which has a more comprehensive implementation adopted from go stdlib;

cli/cli/compose/loader/windows_path.go

Lines 8 to 27 in 91d097e

	// This file contains utilities to check for Windows absolute paths on Linux.
	// The code in this file was largely copied from the Golang filepath package
	// https://github.com/golang/go/blob/1d0e94b1e13d5e8a323a63cd1cc1ef95290c9c36/src/path/filepath/path_windows.go#L12-L65
	func isSlash(c uint8) bool {
	return c == '\\' || c == '/'
	}
	// isAbs reports whether the path is a Windows absolute path.
	func isAbs(path string) (b bool) {
	l := volumeNameLen(path)
	if l == 0 {
	return false
	}
	path = path[l:]
	if path == "" {
	return false
	}
	return isSlash(path[0])
	}

[thaJeztah]

Don't think we can currently consolidate those as they have slightly different semantics (compose allows C:\some-path, C:/some-path, but not /some-path or \\some-path), but possibly something to look into

[laurazard]

LGTM