Panic while parsing Git repository URL from Bitbucket

[patrick246]

Describe the bug

When specifying a Bitbucket repository HTTPS URL as a resource, there is a panic in api/internal/git/repospec.go:128

kustomize/api/internal/git/repospec.go

Line 128 in 0f614e9

if n[0] == '/' {

n is empty while parsing the URL below, therefore it panics when accessing n[0]. This happens in general, when the repository URL ends in .git.

Files that can reproduce the issue
kustomization.yaml

resources:
 - https://bitbucket.example.com/scm/project/repository.git

Expected output
Resources from that repository, or an error message related to the repository not existing.

Actual output

panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
sigs.k8s.io/kustomize/api/internal/git.parseGitUrl(0xc000329380, 0x3d, 0x1, 0x1db0e00, 0xc00033fb80, 0x20, 0x1b74a40, 0x0, 0xc00033fb60, 0xc00029f358, ...)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/internal/git/repospec.go:128 +0x7f7
sigs.k8s.io/kustomize/api/internal/git.NewRepoSpecFromUrl(0xc000329380, 0x3d, 0x15ad005, 0x17c4580, 0xc0003495f0)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/internal/git/repospec.go:89 +0x6a
sigs.k8s.io/kustomize/api/loader.(*fileLoader).New(0xc00035c0f0, 0xc000329380, 0x3d, 0x3d, 0x17c4680, 0xc00033fb80, 0x203000)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/loader/fileloader.go:174 +0x5f
sigs.k8s.io/kustomize/api/internal/target.(*KustTarget).accumulateResources(0xc0002ff340, 0xc00033fb00, 0xc0002ff740, 0x1, 0x4, 0x1b74a40, 0x0, 0xc00029f568)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/internal/target/kusttarget.go:339 +0x144
sigs.k8s.io/kustomize/api/internal/target.(*KustTarget).accumulateTarget(0xc0002ff340, 0xc00033fb00, 0xc00029f600, 0x1431b53, 0x0)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/internal/target/kusttarget.go:163 +0x74
sigs.k8s.io/kustomize/api/internal/target.(*KustTarget).AccumulateTarget(0xc0002ff340, 0x0, 0xffffffffffffffff, 0x0)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/internal/target/kusttarget.go:156 +0xce
sigs.k8s.io/kustomize/api/internal/target.(*KustTarget).makeCustomizedResMap(0xc0002ff340, 0x0, 0x0, 0x0, 0x1)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/internal/target/kusttarget.go:111 +0x2f
sigs.k8s.io/kustomize/api/internal/target.(*KustTarget).MakeCustomizedResMap(...)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/internal/target/kusttarget.go:107
sigs.k8s.io/kustomize/api/krusty.(*Kustomizer).Run(0xc00029fd50, 0x17defa0, 0x1ba5708, 0x7ffeefbff578, 0x1, 0x0, 0x0, 0x0, 0x0)
	/go/pkg/mod/sigs.k8s.io/kustomize/[email protected]/krusty/kustomizer.go:88 +0x3db
sigs.k8s.io/kustomize/kustomize/v4/commands/build.NewCmdBuild.func1(0xc00032a000, 0xc0003485b0, 0x1, 0x1, 0x0, 0x0)
	/workspace/myClone/kustomize/commands/build/build.go:80 +0x1c8
github.com/spf13/cobra.(*Command).execute(0xc00032a000, 0xc000348580, 0x1, 0x1, 0xc00032a000, 0xc000348580)
	/go/pkg/mod/github.com/spf13/[email protected]/command.go:842 +0x47c
github.com/spf13/cobra.(*Command).ExecuteC(0xc00015f8c0, 0x0, 0x1619a40, 0xc00008c058)
	/go/pkg/mod/github.com/spf13/[email protected]/command.go:950 +0x375
github.com/spf13/cobra.(*Command).Execute(...)
	/go/pkg/mod/github.com/spf13/[email protected]/command.go:887
main.main()
	/workspace/myClone/kustomize/main.go:14 +0x2a

Kustomize version
{Version:kustomize/v4.1.3 GitCommit:0f614e92f72f1b938a9171b964d90b197ca8fb68 BuildDate:2021-05-20T20:52:40Z GoOs:darwin GoArch:amd64}

Platform
MacOS 10.15.7

Additional context
Working around this bug is possible, by leaving out the .git at the end, or if not possible, specifying ?ref=master. That should not change the behavior, but it gives the parser something to parse, so the n[0] access is possible.