[REPL] Fix #55850 by using safe_realpath instead of abspath in projname (#55851)

Author: christiangnrd

stdlib/REPL/src/Pkg_beforeload.jl

@@ -88,7 +88,7 @@ function projname(project_file::String)
     end
     for depot in Base.DEPOT_PATH
         envdir = joinpath(depot, "environments")
-        if startswith(abspath(project_file), abspath(envdir))
+        if startswith(safe_realpath(project_file), safe_realpath(envdir))
             return "@" * name
         end
     end

stdlib/REPL/test/repl.jl

@@ -1966,11 +1966,20 @@ end
 
 @testset "Dummy Pkg prompt" begin
     # do this in an empty depot to test default for new users
-    withenv("JULIA_DEPOT_PATH" => mktempdir(), "JULIA_LOAD_PATH" => nothing) do
+    withenv("JULIA_DEPOT_PATH" => mktempdir() * (Sys.iswindows() ? ";" : ":"), "JULIA_LOAD_PATH" => nothing) do
         prompt = readchomp(`$(Base.julia_cmd()[1]) --startup-file=no -e "using REPL; print(REPL.Pkg_promptf())"`)
         @test prompt == "(@v$(VERSION.major).$(VERSION.minor)) pkg> "
     end
 
+    # Issue 55850
+    tmp_55850 = mktempdir()
+    tmp_sym_link = joinpath(tmp_55850, "sym")
+    symlink(tmp_55850, tmp_sym_link; dir_target=true)
+    withenv("JULIA_DEPOT_PATH" => tmp_sym_link * (Sys.iswindows() ? ";" : ":"), "JULIA_LOAD_PATH" => nothing) do
+        prompt = readchomp(`$(Base.julia_cmd()[1]) --startup-file=no -e "using REPL; print(REPL.projname(REPL.find_project_file()))"`)
+        @test prompt == "@v$(VERSION.major).$(VERSION.minor)"
+    end
+
     get_prompt(proj::String) = readchomp(`$(Base.julia_cmd()[1]) --startup-file=no $(proj) -e "using REPL; print(REPL.Pkg_promptf())"`)
 
     @test get_prompt("--project=$(pkgdir(REPL))") == "(REPL) pkg> "