Replace depots()[1] with depots1() where depots1 throws (Pkg PR 563)

a more descriptive error, instead of a BoundsError, in
the case where DEPOT_PATH is empty.

(cherry picked from commit 0ecaf2d,
Julia PR #28443)

stdlib/Pkg/src/Operations.jl

@@ -9,7 +9,7 @@ import LibGit2
 import REPL
 using REPL.TerminalMenus
 using ..Types, ..GraphType, ..Resolve, ..Pkg2, ..BinaryProvider, ..GitTools, ..Display
-import ..depots, ..devdir, ..Types.uuid_julia
+import ..depots, ..depots1, ..devdir, ..Types.uuid_julia
 
 function find_installed(name::String, uuid::UUID, sha1::SHA1)
     slug_default = Base.version_slug(uuid, sha1)
@@ -20,7 +20,7 @@ function find_installed(name::String, uuid::UUID, sha1::SHA1)
             ispath(path) && return path
         end
     end
-    return abspath(depots()[1], "packages", name, slug_default)
+    return abspath(depots1(), "packages", name, slug_default)
 end
 
 function load_versions(path::String)
@@ -480,7 +480,7 @@ function install_git(
     tree = nothing
     try
         repo, git_hash = Base.shred!(LibGit2.CachedCredentials()) do creds
-            clones_dir = joinpath(depots()[1], "clones")
+            clones_dir = joinpath(depots1(), "clones")
             ispath(clones_dir) || mkpath(clones_dir)
             repo_path = joinpath(clones_dir, string(uuid))
             repo = ispath(repo_path) ? LibGit2.GitRepo(repo_path) : begin

stdlib/Pkg/src/Pkg.jl

@@ -12,8 +12,14 @@ export PackageMode, PKGMODE_MANIFEST, PKGMODE_PROJECT
 export UpgradeLevel, UPLEVEL_MAJOR, UPLEVEL_MAJOR, UPLEVEL_MINOR, UPLEVEL_PATCH
 
 depots() = Base.DEPOT_PATH
-logdir() = joinpath(depots()[1], "logs")
-devdir() = get(ENV, "JULIA_PKG_DEVDIR", joinpath(depots()[1], "dev"))
+function depots1()
+    d = depots()
+    isempty(d) && cmderror("no depots found in DEPOT_PATH")
+    return d[1]
+end
+
+logdir() = joinpath(depots1(), "logs")
+devdir() = get(ENV, "JULIA_PKG_DEVDIR", joinpath(depots1(), "dev"))
 const UPDATED_REGISTRY_THIS_SESSION = Ref(false)
 
 # load snapshotted dependencies

stdlib/Pkg/src/Types.jl

@@ -11,7 +11,7 @@ using REPL.TerminalMenus
 
 using ..TOML
 import ..Pkg, ..UPDATED_REGISTRY_THIS_SESSION
-import Pkg: GitTools, depots, logdir
+import Pkg: GitTools, depots, depots1, logdir
 
 import Base: SHA1
 using SHA
@@ -519,7 +519,7 @@ function handle_repos_develop!(ctx::Context, pkgs::AbstractVector{PackageSpec},
                 # We save the repo in case another environement wants to
                 # develop from the same repo, this avoids having to reclone it
                 # from scratch.
-                clone_path = joinpath(depots()[1], "clones")
+                clone_path = joinpath(depots1(), "clones")
                 mkpath(clone_path)
                 repo_path = joinpath(clone_path, string(hash(pkg.repo.url), "_full"))
                 repo = nothing
@@ -597,7 +597,7 @@ function handle_repos_add!(ctx::Context, pkgs::AbstractVector{PackageSpec};
             pkg.repo == nothing && continue
             pkg.special_action = PKGSPEC_REPO_ADDED
             isempty(pkg.repo.url) && set_repo_for_pkg!(env, pkg)
-            clones_dir = joinpath(depots()[1], "clones")
+            clones_dir = joinpath(depots1(), "clones")
             mkpath(clones_dir)
             repo_path = joinpath(clones_dir, string(hash(pkg.repo.url)))
             repo = nothing
@@ -899,7 +899,7 @@ end
 # Return paths of all registries in all depots
 function registries(; clone_default=true)::Vector{String}
     isempty(depots()) && return String[]
-    user_regs = abspath(depots()[1], "registries")
+    user_regs = abspath(depots1(), "registries")
     # TODO: delete the following let block in Julia 1.0
     let uncurated = joinpath(user_regs, "Uncurated"),
         general = joinpath(user_regs, "General")